1. Field of the Invention
This invention relates to a thermoplastic semiconductor package and to a method of making it, and more particularly concerns attaching a thermoplastic lid or cover to a thermoplastic cavity type semiconductor package body by ultrasonic welding. The semiconductor package may be a Plastic Quad Flat Pack package (PQFP) as shown in FIGS. 1 and 11, Plastic Dual In-Line Package (PDIP) as shown in FIGS. 3 and 13, or a Plastic Pin Grid Array package (PPGA) as shown in FIG. 5, and may include Small Outline Integrated Circuit (SOIC) variations, but is not limited thereto. The semiconductor package may include single or multiple Integrated Circuit (IC) arrangements.
The term "Plastic Cavity Type Semiconductor Package" refers to any type of semiconductor package that provides for the mounting of an integrated circuit die onto the die pad of the semiconductor package through a recess or cavity in the semiconductor package, subsequently adding electrical interconnections and sealing the electrical components by applying a sealant over the wires and die.
The terms "lid" or "cover" as used in this disclosure are interchangeable, and refer to any component that is attached to the main body of a semiconductor package to protect the internal components of the semiconductor package, such as the integrated circuit, from environmental or physical damage or contamination. The design of the lid may be such to fit within the constraints of a cavity in the semiconductor package body. Alternatively, if desired, the lid may be an integral component of the overall cover of the device. The term lid does not define top or bottom.
The term "ultrasonic welding" refers to a method of welding elements together by producing an intense, controlled vibration from an ultrasonic welding booster horn and applying it to the elements to be welded. This intense controlled vibration, coupled with an application of a set pressure against the components to be welded, develops frictional heat which causes melting of one or both of the components at the interface between the components, and creates a mechanical bond between the components.
A plastic cavity type semiconductor package is a practical vehicle for the mounting of a subminiature integrated circuit to printed circuit or wiring board. Plastic cavity-type semiconductor packages contain an integrated circuit which is electrically interconnected to an integral polyester, epoxy or polyimide resin base laminated substrate with an integral electrical circuit, or to an integral conductive lead frame. The substrate circuit or lead frame enlarges the effective pitch, or spacing, between electrical connections of the integrated circuit to a practical, useable dimension found on printed circuit or wiring boards. The method of enlargement may be by a flexible or rigid substrate circuit, a stamped or chemically etched conductive lead frame, or a combination of a substrate circuit and a conductive lead frame.
The ways of mounting a plastic cavity type semiconductor package onto a printed circuit or wiring board varies from insertion or through hole mounting to surface mounting.
The particular way of mounting dictates the arrangement of the electrical leads that interface with the printed circuit or wiring board.
The method of pitch enlargement typically utilized for Plastic Quad Flat Pack (PQFP) and Plastic Dual In-Line Packages (PDIP) ma be either an integral substrate circuit electrically connected to the internal ends of a lead frame, whereby the external ends of the lead frame interface the printed circuit or wiring board, or an integral lead frame whereby the integrated circuit is electrically connected to the internal ends of the lead frame and the external ends interfacing the printed circuit or wiring board. The interface may be a surface mount or insertion type interface.
The method of enlargement typically utilized for a Plastic Pin Grid Array, (PPGA) may be an integral substrate circuit electrically connected to the internal ends of a conductive pin, whereby the pins form a matrix pattern and provide electrical connection to the printed circuit or wiring board by inserting the external ends of the conductive pin matrix into the printed circuit or wiring board.
Upon mounting the integrated circuit or die onto the die pad, a series of wire interconnections, or wire bonds, are made between the integrated circuit and the internal leads of a lead frame, or to a substrate circuit. In applications requiring sealed integrated circuits, a sealant is applied on and about the integrated circuit and the wire bond interconnections.
Plastic cavity type semiconductor packages are offered in various formats. Plastic Pin Grid Arrays, PPGA, for example, are available in a bare substrate circuit and pin matrix in which all the components compromising the semiconductor package are visible. A cavity, or recess, is designed into the substrate circuit for mounting of an integrated circuit die.
The PPGA is also available with the substrate circuit, and the interface of the pin matrix and the substrate circuit, pre-molded or encapsulated with a plastic molding compound. A cavity is designed into this package body for mounting an integrated circuit die and for electrically interconnecting the die to the substrate circuit.
The end user provides for the integrated circuit die mounting, the electrical interconnection of the integrated circuit to the substrate circuit and the protection of the integrated circuit by the application of a sealant or lid onto the semiconductor package.
In the case of a bare semiconductor package, a typical method of providing protection to the integrated circuit and electrical interconnection against environmental or physical damage involves the total encapsulation of the bare package with a molding compound, or the application of a "Blob Top", by placing a suitable quantity of sealant, in the cavity on top of the integrated circuit and electrical interconnections, and curing the sealant by applying heat or ultraviolet rays.
In the case of the pre-molded or encapsulated cavity package, a typical method of providing protection to the integrated circuit and electrical interconnection involves applying a "Blob Top" or attaching a lid over the cavity. In a typical lidding process, a suitable amount of adhesive is applied about the cavity opening or on the lid or, in some cases, both. The lid and package body are then mated together and allowed to cure by applying heat or ultraviolet rays. The actual application of the adhesive may be by dispensing a liquid material, screen printing a paste material, or applying a preformed adhesive material blank onto the components to be mated.
The disadvantages of the current methods of protecting the integrated circuit in a Plastic Cavity-Type Semiconductor Package include the following:
a Adhesive bonding of the lid to the semiconductor package is a time consuming process that involves subjecting the assembly to possible contamination by the adhesive bonding agents. PA1 b. Adhesive bonding agents, and sealing agents, curable by any method, are hydroscopic compounds which absorb moisture, and this moisture is introduced into the cavity and onto the electrical components, causing corrosion and failure. PA1 c. Moisture within a lidded plastic cavity semiconductor package causes an increase in pressure within the cavity when subjected to elevated temperatures, such as soldering. The increase in pressure, due to the expansion of the moisture, raises internal pressures to a level which may cause the lid to separate from the assembly. PA1 d. Encapsulation, or Blob Topping, is a time consuming process which involves subjecting the assembly to possible contamination by the sealing agent, possible failure of the assembly due to moisture introduction, and possible failure of the assembly due to thermal induced stress, and may cause separation or disconnection of the wire bond from the integrated circuit, or separation of the electrical interconnection to the semiconductor package. Heat curing of the sealant also causes thermal induced stress. PA1 e. Over molding semiconductor packages with a plastic mold compound involves subjecting the assembly to possible wire sweeping, which occurs during the injection of the plastic molding compound. Wire sweeping may cause shorting between adjacent wire bonds, or may cause separation or disconnection of the wire bonds from the integrated circuit, or the electrical interconnection to the semiconductor package. PA1 f. Stress critical integrated circuits may not be subjected to multiple cycles of elevated temperature, as the integrated circuit may crack or disconnect from the die mount surface. Failures due to stress cracking are increased by thermal cycling. An example of multiple thermal cycling: Die attaching requires the introduction of heat to cure the bonding agent, and Blob Topping requires heat to cure the sealant, and over molding, which is performed at elevated temperatures. PA1 g. Additional handling of a semiconductor package during the process of adhesive bonding or sealing involves subjecting the assembly to possible contamination or physical damage which may cause failure. PA1 h. A major disadvantage in the assembly of an over-molded or blob topped semiconductor package is noticed during thermal cycling. The differences in the coefficients of thermal expansion, the rate in which a material expands or contracts in response to temperature changes, of the integral components, i.e., the die, the die attach agents, the wire interconnections, the encapsulation material, and so on, are such that when the assembly is subjected to thermal cycling, multiple exposures to hot and cold temperatures, the components expand or contract at different rates. Thermal cycling causes stress and/or strain upon the components due to the differences in those rates and may cause component failure due to wear out, disassociation of surfaces, or fractures of the integral components. Also, the larger dies which are now utilized, include integral fine line geometry. During thermal cycling, the differences in thermal expansion may cause the fine line geometry to crack or separate due to the stresses upon the die surface caused by the expansion of the encapsulation material against the die surface. This is an increasing occurrence due to the increased use of large, fine line geometry, stress critical dies. Another disadvantage of thermal cycling and the problem associated with thermal expansion, is the additional potential for failure due to corrosion or lid separation. As the integral components expand and/or contract during thermal cycling, pockets or voids are created. These pockets or voids allow moisture to gather. Moisture within a semiconductor package causes failures due to corrosion or increase in internal package pressure.


Communication networks increasingly carry information at various data rates. The selected data rate for a given communication can be pre-established between the transmitter and receiver, can be signaled, for example, using handshaking techniques, or can by dynamically determined by the receiver. Data rate detection techniques allow a receiver to determine the rate of incoming data, for example, by examining the received data. Such automatic data rate detection techniques allow a receiver to receive data from a variety of transmitting devices operating at different speeds without having to establish data rates in advance
Signals arriving at a receiver are typically corrupted by intersymbol interference (ISI), crosstalk, echo, and other noise. In order to compensate for such channel distortions, communication receivers often employ well-known equalization techniques. For example, zero equalization or decision-feedback equalization (DFE) techniques (or both) are often employed. Such equalization techniques are widely-used for removing intersymbol interference and to improve the noise margin. See, for example, R. Gitlin et al., Digital Communication Principles, (Plenum Press, 1992) and E. A. Lee and D. G. Messerschmitt, Digital Communications, (Kluwer Academic Press, 1988), each incorporated by reference herein Generally, zero equalization techniques equalize the pre-cursors of the channel impulse response and decision-feedback equalization equalizes the post cursors of the channel impulse response.
A communication channel typically exhibits a low pass effect on a transmitted signal. The various frequency components of a signal will thus encounter different attenuation at the output of the channel, with higher frequency components of a transmitted signal being impaired more than lower frequency components. Thus, the impairment of a channel is said to be rate-dependent. As a result, the equalization parameters optimized for one data rate will typically not be applicable for another data rate
In the absence of a received signal, the receiver lacks information (data transitions) and cannot sustain a frequency lock. If the equalizer is allowed to train when the signal has been lost, the equalizer will produce invalid updates Likewise, there are a number of predefined patterns that are not sufficiently spectrally rich to provide valid equalization results. For example, many communications systems continuously send an idle pattern to keep the system alive, in a similar manner to a heart beat signal. The idle pattern, however, is not spectrally rich and is therefore not good for equalization.
A need therefore exists for rate-dependent methods and apparatus for equalizing a channel A further need exists for equalization methods and apparatus that can detect the data rate, and perform equalization based on the detected data rate. Yet another need exists for equalization methods and apparatus that update the equalization parameters only if one or more predefined qualifier conditions, such as a loss of signal, are not present.


Field of the Disclosure
This application relates, in general, to a wake system for a watercraft, and more particularly, to a surf wake system for modifying a wake produced by a watercraft travelling through water.
Description of the Related Art
Wake surfing has become increasingly popular in recent years because, unlike an ocean wave, a wake produced by a watercraft is on-demand not to mention continuous and endless as long as the watercraft is moving forward. As a watercraft travels through water, the watercraft displaces water and thus generates waves including bow wave and diverging stern waves on both sides of the watercraft. Due to pressure differences, these waves generally converge in the hollow formed behind the traveling watercraft and/or interfere with each other to form a wake behind the watercraft. Such a wake, however, is generally small, choppy or too close to the watercraft to be suitable and safe for water sports, and particularly not suitable for wake boarding or surfing.
To facilitate surfing, a wake should be formed away from the stern of the watercraft, for example, about ten feet away, and with a waist-height peak, for example, about three feet or higher. Generally hundreds, and sometimes thousands, of pounds of additional weight or ballast to a rear corner of the watercraft to make the watercraft tilt to one side, displaces more water, and hence generates a larger wake on that side. Such additional weight may be in the form of removable ballast bags, installed ballast tanks or bladders, or passengers positioned to one side of the watercraft, which is primarily used to tip the watercraft to that side. Using such additional weight to produce larger wakes, however, poses several disadvantages. For example, such additional weight may take up significant space and capacity that may otherwise reduce the passenger capacity of the watercraft. Also, such additional weight may unbalance the watercraft creating difficulties in control. Moreover, the additional weight generally must be moved from one side of the water craft to the other in order to generate a wake on the other side of the water craft. Shifting such additional weight may require significant time and effort. For example, filling and emptying ballast tanks to switch from one side to the other may require 20 minutes or more.
Alternatively, it is known to require extensive modification to a boat hull to promote a proper surf wake. An exemplar of generating a larger wake can be found in a U.S. Pat. No. 6,105,527 to Lochtefeld et al.
In light of the foregoing, it would therefore be useful to provide surf wake system that overcomes the above and other disadvantages.


In typical industrial plants and food processing facilities, safety practices such as human hazard reporting and safety observation tours (SOTs) address safety hazards as they are identified and dealt with. However, despite these efforts, accidents, near misses, and contamination issues still occur. Often, safety issues are addressed with quick fixes that result in corrosion of metal, overstressing of electrical systems, and other conditions that eventually lead to equipment malfunctions and new safety hazards. Further, while some facilities may include sensors to identify specific, isolated safety concerns, such as ingress of liquid past a predefined boundary or electrical overloads, complex and slowly developing safety issues at an industrial site may go unnoticed.


The invention relates generally to spherical-shaped semiconductor integrated circuit manufacturing systems, and more particularly, to a fluid exchange system, suitable for use in such manufacturing systems, for purging a first fluid from a process flow comprised of the first fluid and spherical-shaped semiconductors and injecting a second fluid into the process flow.
Conventional integrated circuits, or "chips," are formed from a flat surface semiconductor wafer. The semiconductor wafer is first manufactured in a semiconductor material manufacturing facility and is then provided to a fabrication facility. At the latter facility, several layers are processed onto the semiconductor wafer surface. Once completed, the wafer is then cut into one or more chips and assembled into packages. Although the processed chip includes several layers fabricated thereon, the chip still remains relatively flat.
A fabrication facility is relatively expensive due to the enormous effort and expense required for creating flat silicon wafers and chips. For example, manufacturing the wafers requires several high-precision steps including creating rod-form polycrystalline semiconductor material; precisely cutting ingots from the semiconductor rods; cleaning and drying the cut ingots; manufacturing a large single crystal from the ingots by melting them in a quartz crucible; grinding, etching, and cleaning the surface of the crystal; cutting, lapping and polishing wafers from the crystal; and heat processing the wafers. Moreover, the wafers produced by the above processes typically have many defects which are largely attributable to the difficulty in making a single, highly pure crystal due to the above cutting, grinding and cleaning processes as well as due to the impurities, including oxygen, associated with containers used in forming the crystals. These defects become more and more prevalent as the integrated circuits formed on these wafers become smaller.
Another major problem associated with modern fabrication facilities for flat chips is that they require extensive and expensive equipment. For example, dust-free clean rooms and temperature-controlled manufacturing and storage areas are necessary to prevent the wafers and chips from defecting and warping. Also, these types of fabrication facilities suffer from a relatively inefficient throughput as well as an inefficient use of the silicon. For example, facilities using in-batch manufacturing, where the wafers are processed by lots, must maintain huge inventories to efficiently utilize all the equipment of the facility. Also, because the wafers are round, and the completed chips are rectangular, the peripheral portion of each wafer cannot be used.
Still another problem associated with modern fabrication facilities is that they do not produce chips that are ready to use. Instead, there are many additional steps that must be completed, including cutting and separating the chip from the wafer; assembling the chip to a lead frame which includes wire bonding, plastic or ceramic molding and cutting and forming the leads, positioning the assembled chip onto a printed circuit board; and mounting the assembled chip to the printed circuit board. The cutting and assembly steps introduce many errors and defects due to the precise requirements of such operations. In addition, the positioning and mounting steps are naturally two-dimensional in character, and therefore do not support curved or three dimensional areas.
Therefore, due to these and various other problems, only a few companies in the world today can successfully manufacture conventional flat chips. Furthermore, the chips must bear a high price to cover the costs of manufacturing, as well as the return on initial capital and investment.
In co-pending U.S. Pat. No. 5,955,776 filed on May 16, 1997, assigned to the same assignee as the present application and hereby incorporated by reference as if reproduced in its entirety, a method and apparatus for manufacturing spherical-shaped semiconductor integrated circuits is disclosed. As disclosed in the aforementioned patent application, the manufacturing process by which a spherical-shaped semiconductor integrated circuit is produced may include a variety of processing steps. Among these are: de-ionized water cleaning, developing and wet etching; diffusion, oxidation and deposition of films; coating; exposure; plasma etching, sputtering and ion implantation; ashing; and epitaxial growth. Many of these steps involve exposing a spherical-shaped semiconductor to a process fluid. For example, a film having a desired composition and thickness may be formed on the surface of the spherical-shaped semiconductors by exposing the spherical-shaped semiconductors to a first process fluid, typically, a gas, having a selected composition at a selected pressure and temperature. To ensure that formation of spherical-shaped semiconductor integrated circuits proceeds as designed, when such a process step is complete, it is often advisable to remove the first process fluid from further contact with the spherical-shaped semiconductors, for example, using a purging process. Failure to do so may result in unwanted chemical reactions, for example, the deposition of an overly thick layer of material, on the surface of the spherical-shaped semiconductors. Additionally, as the manufacturing process for spherical-shaped semiconductor integrated circuits often incorporates a multitude of processing steps such as the ones previously described, to aid in the efficiency of the manufacturing process and/or to assist in the transport of the spherical-shaped semiconductors between processing stations, it is often desirable to replace the removed process fluid with a second process fluid.
Further complicating the manufacturing process for spherical-shaped semiconductor integrated circuits are the special handling requirements which must be afforded the circuits during the manufacture thereof. Unlike conventional integrated circuits formed from flat surface semiconductor wafers, the spherical-shaped semiconductor integrated circuits produced from spherical-shaped semiconductors consume the entire surface area of the spherical-shaped semiconductors. Thus, unlike conventional integrated circuits which may be grasped along bottom or side surfaces thereof, grasping or otherwise contacting spherical-shaped semiconductor during the manufacturing process may result in significant damage thereto. Thus, many of the processing techniques used to manufacture conventional integrated circuits are unsuitable for use in the manufacture of spherical-shaped semiconductor integrated circuits.
Thus, it would be desirable to provide a fluid exchange system, capable of purging a first fluid from and injecting a second fluid into a process flow, suitable for use in spherical-shaped semiconductor integrated circuit manufacturing processes. It is, therefore, the object of the invention to provide such a fluid exchange system.


Currently there are various kitchen appliances using electric motors. Some kitchen appliances desire the electric motor to be smaller without reducing its power. One such kitchen appliance is the food processor.
Conventionally, the food processor uses a two-pole universal motor. The stator of the motor has a stator core which includes a yoke with a rectangular configuration and two salient poles which extend inwardly from two opposing sides of the yoke and have stator windings wound thereon. When the stator windings are electrified, two magnetic poles with opposite polarity are formed at the salient poles and two magnetic circuits are formed. Each magnetic circuit passes through two stator poles, the rotor and a side of the yoke so that it has a relatively long path.
The present invention aims to provide a new kitchen appliance, especially a food processor which is permitted to be smaller and cheaper.


1. Field of the Invention
The present invention pertains to a method for disposing of slurried and sometimes toxic solids wastes in hydraulically fractured subterranean earth formations and in such a way that the waste material is confined in the fracture.
2. Background
Certain types of solid waste material may be permanently stored or disposed of by forming a slurry of solids particulates of the waste with a carrier liquid, reducing the particle size of the solids and then injecting the slurry into a subterranean earth formation. U.S. Pat. No. 5,129,469 to J. E. Jackson, issued Jul. 14, 1992, assigned to the assignee of the present invention, and incorporated herein by reference describes a system for disposing of drill cuttings from drilling wells in earth formations by combining the cuttings with a carrier liquid, grinding the cuttings to a predetermined particle size and injecting the viscous slurry of cuttings and carrier liquid which results from the grinding operation into a subterranean earth formation zone.
Certain problems arise, however, with respect to the disposal of certain types of wastes wherein the containment of the waste material in a particular portion of an earth formation zone is required. In the production of oil and gas, for example, a significant amount of naturally occurring radioactive material (NORM) may accumulate in the conduits and processing vessels associated with the production wells and related fluid handling facilities. The radioactive parts of these naturally occurring radioactive materials are usually Radium.sup.226 and/or Radium.sup.228. These radioactive substances are usually bound within the structure of scales and other produced solids. Typically, the composition of the scale is in the form of barium sulfate which is particularly hard and cannot be dissolved by most naturally occurring fluids. Accordingly, this barium sulfate scale, as well as other materials which are mixed with the scale, presents a disposal problem because of its radioactivity.
Certain techniques for disposing of solids-laden slurries in subterranean formations are described in U.S. patent application Ser. No. 08/032,951 filed Mar. 17, 1993, by Thomas K. Perkins, et. al now U.S. Pat. No. 5,314,265, issued May 24, 1995, and assigned to the assignee of the present invention. This application describes a method of disposing of slurries of relatively fine particles of solid wastes into disposal zones which have a lower in situ compressive stress than that of an overburden zone and an underburden zone adjacent to the disposal zone. The disposal zone preferably has a permeability greater than the overburden and underburden zones. This technique is advantageous in that it is common to find earth formations having one or more relatively permeable zones of substantial thickness which are located below a formation zone comprising overburden of relatively impermeable material and which may exhibit in situ compressive stresses generally greater than the more permeable zone.
U.S. patent application Ser. No. 08/043,323 filed Apr. 6, 1993, by Joseph H. Schmidt, et. al now U.S. Pat. No. 5,387,737, issued Feb. 7, 1995, and assigned to the assignee of the present invention describes a method of disposing of particulate solids in a subterranean formation by injecting a quantity of substantially solids-free liquid into a predetermined disposal zone having a predetermined porosity such that the injection of the solids-free liquid disaggregates at least part of the disposal zone, and then injecting a slurry of particulate solids into the disaggregated part of the disposal zone to place the solids in the pore spaces of the disaggregated part of the disposal zone. Other techniques which are of interest but which are not suitable for disposing of toxic wastes in accordance with the present invention are disclosed in U.S. Pat. No. 3,292,693 issued Dec. 20, 1966 to G. A. Hill, et. al, which describes a technique of disposing of liquid wastes into a low pressure zone in an earth formation which is between higher pressure zones and wherein liquids in the higher pressure zones tend to migrate toward the low pressure zone.
Still further, Australian Patent 233,971, published Mar. 3, 1960 by J. J. Reynolds, et al, describes a method of underground disposal of radioactive liquids or slurries wherein a substantially horizontal fracture is created in a shale or nominally non-porous rock formation by opening the fracture with a suitable fracturing fluid and then injecting a radioactive waste material and propagating the fracture by injecting the radioactive fluid at a pressure greater than the formation breakdown pressure. Although generally horizontal fractures were thought to be the type of fracture typically formed in a subterranean earth formation according to the state of the art in 1960, it is generally accepted presently that fractures tend to extend in generally vertical planes under the urging of hydraulic or similar fluid injections. Moreover, totally non-porous or non-permeable formations may exist but they are difficult to locate and are usually not readily accessible for disposal operations.
Notwithstanding the foregoing methods for disposing of slurries of waste materials, the present invention provides a method for disposing of toxic wastes, including radioactive materials, in an improved way which substantially satisfies the requirement of containment of the waste in a predetermined earth formation zone.


On-demand delivery of audiovisual content or other media content over broadband services may involve delivery of very large media files over broadband connections of varying speed and stability. Because available bandwidth may vary with network usage, location of the receiving device relative to a host or a server, and other factors, a delivery method that may be appropriate for one user at one location and at one particular time may not be satisfactory for another user at a different location or at a different time.
For example, while a first user at a first location may be able to stream motion video media content at high resolution at any time of day or night without playback stoppages, a second user at a second location may be able to satisfactorily stream motion video content only during low usage hours. During higher usage hours, the second user may instead download media content to avoid frequent playback stoppages. Progressive downloading, in which metadata about the media file is stored in the first part of the file to be transmitted, allows playback to begin before all of the media content is fully downloaded. Like streaming, however, progressive downloading permits the start of playback usually only after a certain portion of the media content has already been received in hopes of avoiding playback stoppages.
An additional problem arises when, during the delivery of the media file via streaming or downloading, the condition of the communication connection changes. For example, at a location where streaming was available at one time, increasing network usage or other changes affecting the communication connection may prevent satisfactory streaming. Conversely, it is possible that at a second location and at a second time, satisfactory streaming may not have been available but may become available.


This invention relates generally to an implantable containment apparatus made of selectively permeable material. In particular, the implantable containment apparatus is used to contain a therapeutical device, such as a drug delivery device, a cell encapsulation device, or a gene therapy device. A therapeutical device can be easily placed and replaced in an apparatus of the present invention without damaging tissues associated with the selectively permeable material of the apparatus.
Various implantable therapeutical devices, such as drug delivery, gene therapy, and cell encapsulation devices, have been disclosed over the years. A common feature of most of these devices is the use of selectively permeable, or semi-permeable, membranes to construct all or part of the device. These membranes contain their respective therapeutic agents and delivery systems within the particular device while being permeable to the desired therapeutical product. For cell encapsulation devices, the membranes are also permeable to life sustaining substances and to cellular waste products.
When implanted in a recipient, the typical biological response by the recipient to most of these therapeutical devices is the formation of a fibrotic capsule around the device. With most drug delivery and gene therapy devices, this can limit the performance of the device, particularly when the therapeutic agent has a short half-life. For cell encapsulation devices, a fibrotic capsule encasing the device most often deprives the encapsulated cells of life sustaining exchange of nutrients and waste products with tissues of a recipient. The result is usually fatal to the encapsulated cells. Furthermore, a fibrotic capsule encasing a therapeutical device usually makes surgical retrieval of the device difficult.
When certain therapeutical devices are implanted in a recipient, predominantly vascular tissues of the recipient can be stimulated to grow into direct, or near direct, contact with the device. On one hand, this is desirable because the therapeutical product of the device can then be delivered directly to the circulation of the recipient through the vascular tissues that are in contact with the device. On the other hand, this is undesirable because once vascular tissues of a recipient have grown in contact with one of these implantable therapeutical devices, removal of the device requires surgical dissection of the tissues to expose and remove the device. Surgical dissection of vascular tissues, particularly capillary tissue, can often be a difficult and painful procedure. Whether encased in a fibrotic capsule or surrounded with vascular tissue, the problem of retrieving these implanted devices is a considerable drawback of the devices.
For cell encapsulation devices, an alternative to retrieving and replacing the entire device in a recipient is to retrieve and replace the cells contained in the device. U.S. Pat. No. 5,387,237, issued to Fournier et al., is a representative example of a cell encapsulation device that has at least one opening into the device through which cells can be introduced and removed. Cells are introduced and removed in this, and other similar devices, as a suspension or slurry. Since most cell encapsulation devices are intended to correct a metabolite deficiency in a recipient caused by dysfunction or failure of certain of the recipient""s cells, tissues, or organs, the source of the replacement cells is rarely the recipient. In a situation where non-autologous cells are used in this type of cell encapsulation device, the problem of contaminating a recipient with the foreign cells during loading, removal, or refilling of the device is ever present. One solution to this contamination problem would be to enclose the cells in a container that can be placed, removed, and replaced in a device as a unit.
A retrievable cell encapsulation envelope enclosed in an implantable permselective membrane for use as an artificial endocrine gland is disclosed in U.S. Pat. No. 4,378,016 issued to Loeb. The Loeb device comprises a housing made of an impermeable hollow stem and a permselective membrane sack. The hollow stem has a distal end defining an extracorporeal segment, a percutaneous segment in the mid-region, and a proximal end defining a subcutaneous segment. The sack is adapted to receive an envelope containing hormone-producing cells and has an access opening that is coupled to the proximal end of the hollow stem. In a preferred embodiment, the cell containing envelope is in the form of a flexible collar. The flexible collar is partially collapsible to allow for easier placement and replacement of the envelope in the sack. Once in place, the flexible collar also provides a snug fit between the envelope and the sack. Placement and replacement of a cell containing envelope in the sack portion is accomplished manually with forceps, or the like. Retrieval of the envelope from the sack can be aided with a guidewire attached to the envelope. In one embodiment of the Loeb device, the sack has openings at both ends that are implanted percutaneously. In this embodiment, the cell containing envelope may be inserted or removed through either end of the device.
The housing of the Loeb device is surgically implanted in a recipient through the abdominal wall so the distal end of the stem protrudes from the recipient, the proximal end of the stem resides subcutaneously with respect to the abdominal wall, and the sack portion is placed in the peritoneal cavity surrounded in peritoneal fluid. According to Loeb, the sack allows hormones, nutrients, oxygen, and waste products to flow in and out of the sack while preventing bacteria from entering the patient. The sack and the envelope are said by Loeb to be permeable to nutrients and hormones, but impermeable to the hormone-producing cells and immune response bodies. Upon implantation of the device in a patient, the cells contained therein are said to take over the function of the corresponding natural gland, sense the amount of hormone needed, and produce the correct amount of the desired hormone.
Implanted cell encapsulation devices, particularly those intended as an artificial endocrine gland, usually require a high rate of flux of nutrients and waste products between the encapsulated cells in the device and tissues of the recipient. Having a cell encapsulation device in close, or direct, association with a vascular structure usually provides the highest rate of nutrient and waste product flux for such a device. Loeb does not teach the value of vascularization of the sack portion of the housing, however. Nor is the Loeb device implanted in a part of the body that is particularly vascularized.
Brauker et al. disclose a cell encapsulation device in U.S. Pat. No. 5,314,471 that requires close association of host vascular structures with the device. According to Brauker et al., xe2x80x9cconventional implant assemblies and methodologies usually fail to keep the implanted cells alive long enough to provide the intended therapeutic benefit.xe2x80x9d Cell death in these implanted devices is said by Brauker et al. to be due in large part to an ischemia imposed on the cells during the first two weeks following implantation. Brauker et al. conclude that xe2x80x9cthe cells die because conventional implant assemblies and methodologies themselves lack the innate capacity to support the implanted cells"" ongoing life processes during the critical ischemic period, when the host""s vascular structures are not nearby.xe2x80x9d Brauker et al. state that in order for implanted cells to survive and function on a long term basis, the host must grow new vascular structures in association with the device. Brauker et al. note that a host will not naturally provide new vascular structures to an implanted cell encapsulation device. According to Brauker et al., the host must be stimulated by the implant assembly itself to grow new vascular structures close to the cell encapsulation device. Angiogenic stimulus can be provided by angiogenic factors applied to the cell boundary of the Brauker et al. device or by certain cell types encapsulated in the device. Growth of vascular tissue in association with a device of Brauker et al. will make removal of the device from a host difficult, however,
An implantable containment apparatus made of selectively permeable polymeric material that permits a therapeutical device, such as a drug delivery, a gene therapy, or a cell encapsulation device, to be placed and replaced in a recipient without damaging or disturbing tissues associated with the selectively permeable polymeric material would be useful. Such an apparatus that becomes closely associated with vascular structures without the need to supply angiogenic factors to induce the close vascularization would also be useful. A method of easily placing and replacing a therapeutical device in an implantable containment apparatus of the present invention would be further useful.
The present invention is directed to an implantable containment apparatus for a therapeutical device, such as a drug delivery device, a cell encapsulation device, or a gene therapy device. The apparatus is primarily made of selectively permeable material. The selectively permeable material permits flux, or exchange, of solutes between a therapeutical device contained in the apparatus and tissues of a recipient, while excluding cells from growing beyond a desired point through the material. When an apparatus is implanted in a recipient, various tissues from the recipient grow to associate with the apparatus. These tissues grow next to, or partially through, the exterior surface of the apparatus. It is preferred that vascular tissue is the predominant tissue that grows to associate with an apparatus of the present invention. Once growth of a recipient""s tissues in association with an apparatus of the present invention has occurred, a therapeutical device can then be easily placed and replaced in the apparatus without damaging or disturbing the tissues associated with the selectively permeable material of the apparatus.
This is preferably accomplished by providing an implantable containment apparatus for a therapeutical device comprising a selectively permeable microporous polymeric material in the form of a tube wherein the tube comprises an exterior surface, an interior surface that defines a luminal space of substantially uniform diameter, and an access means at one end of the tube through which a therapeutical device is insertable into the luminal space of the tube wherein, once a therapeutical device is inserted into the luminal space of the tube, the therapeutical device is retained within the tube wherein biochemical and therapeutic substances having a molecular weight up to about 5,000,000 MW diffuse across the thickness of the tube between the contents of the therapeutical device contained therein and tissues of a recipient wherein the therapeutical device is removable from the tube through the access means of the tube and wherein the tube is refillable with a therapeutical device through the access means of the tube. The apparatus can also have an access means at each end of the tube. In this embodiment, a therapeutical device can be inserted and removed from the luminal space of the tube through either access means in the tube. Furthermore, in this embodiment, a fluid stream can be established through both access means of the tube that can then be used to flush a therapeutical device in and out of the luminal space of the tube.
Accordingly, the present invention is also directed to a method in which a therapeutical device, such as a drug delivery device, a gene therapy device, or a cell encapsulation device, is easily inserted into, removed from, and replaced in a containment apparatus of the present invention as a unit with a fluid stream. The method involves repeatedly filling and emptying an implantable containment apparatus tube with a therapeutical device.
Other features and advantages of the invention will become apparent upon review of the following specification, drawings, and claims.


1. Field of the Invention
This invention relates generally to bed structures for hauling; and more particularly, to a light-weight structure having improved clamp-down and tie-down mechanisms adjustably positioned thereon.
2. State of the Prior Art
Various structures for supporting and transporting snowmobiles, all terrain vehicles, garden tractors, motorcycles, and the like have been described. Many of these structures are associated with trailers that can be towed behind a vehicle. Many general hauling structures included fixed tie-down devices around the periphery of the bed that are utilized in conjunction with chains, ropes, elastic style hooked tie-down devices, or retractable web tie-down material. Tying objects or various types of recreational vehicles in this manner is time consuming, inconvenient, and in many instances unsafe and inadequate.
Various types of specialty tie-down and clamp-down devices have been developed to be utilized in conjunction with specific objects. For example, various types of snowmobile trailers have bar structures that can be affixed across the tops of the snowmobile skis and are affixed to the edge frame of the trailer structure. These devices characteristically are in fixed position and do not accommodate a snowmobile being at various locations along the length of the bed. In some cases portions of the frame are adapted to receive part of skis and retain them. These arrangements are lacking in versatility, and in some cases do no adequately restrain the vehicles.
Certain types of trailers utilized for transporting motorcycles and the like have a longitudinal channel in which the wheels are placed to prevent the wheels from sliding sideways, and the tie-down is accomplished by various devices as mentioned above. While assisting the positioning of the motorcycle, these channels substantially impair the use of the trailer for any other function, and do nothing to prevent the forward and backward motion of the motorcycle.
Many of the transport beds are constructed of a supporting frame to which a deck or bed is affixed. Various structures and devices have been utilized to affix the bed to the frame, including bolts, clamps, screws and sundry fixtures and fasteners. The prior art type of fastening is costly in assembly and does not readily allow replacement of worn or damaged bed material. An improvement has been recognized in the prior art wherein side structural members have channels in which the bed material can be inserted and supported along its length. These prior art arrangements generally only deal with the entire bed and require substantial additional fastening structures across the width of the bed to the various frame support members. Such structures are not readily repairable or replaceable even with the sliding channels at the sides.
It is a primary objective of this invention to provide an improved transport bed structure.
Yet another objective is to provide a transport bed that has improved clamp-down and tie-down mechanisms.
Still a further object of the invention is to provide a rotatable telescoping clamp-down mechanism.
Another objective of the invention is to provide an improved clampdown mechanism operable in conjunction with a retention channel for variable placement.
Still a further object is to provide an improved tie-down mechanism operable with a retention channel.
A further object of the invention is to provide an improved bed mounting structure.
Still a further object of the invention is to provide bed mounting structures that minimize the cost of construction and maximize the ease of repair and replacement.
Another object of the invention is to provide improved clamp-down and tie-down mechanisms that are light-weight, durable, and relatively maintenance free.
These and other more detailed and specific objectives will become apparent from a consideration of the following description of the invention.
The present invention includes a bed structure utilized for transporting objects, and includes an improved clamp-down mechanism. One aspect of the improved clamp-down mechanism involves a telescoping clamping member that is associated with an elongated retention channel integrated as part of the bed structure, where the telescoping clamp mechanism can be selectively positioned along the length of the retention channel and utilized to clamp at various locations on the bed. One or more retention channels may be utilized in a spaced apart relationship. The telescoping clamp members can be retracted and rotated for installation into the clamp position and for releasing from the clamp position.
A tie-down mechanism can also be used within the same retention channels and is likewise subject to variable positioning along the retention channel to form a tie-down relationship with an object.
The telescoping clamp-down mechanism and the tie-down mechanism are each retained in the retention channel by a rotatable cam that hold the mechanisms in the retention channel in a first position and allows them to be removed from the retention channel in a second position.
The retention channels and the structural frame members are adapted to have bed retaining channels along their lengths to support, retain, and protect the edges of the bed material without additional clamps or fastening mechanisms.
The rear frame member generally has a channel cross-section and is adapted for mounting lights within the channel recess to protect them from damage. In one configuration the rear member has a lower limit or lip portion for protecting the rear frame member if the associated bed structure is lowered to contact the surface for loading. The upper portion of the rear frame member includes a predetermined number of protrusions extending along the length thereof. A slidably engagable ramp structure is adapted with a longitudinal channel configured to match the arrangement of longitudinal protrusions on the rear frame member. The ramp member is slidably attached to the rear frame member when the bed structure has been put in place, and is adapted to retain and protect the rear edge of the bed. The ramp structure is sloped to allow ease of loading from the rear when the bed structure is utilized with a tiltable supporting structure.
All of the component parts are integrally formed from extruded light-weight material and cut to lengths required for assembly, there providing an efficient and cost-effective manufacturing system for various sizes of bed structures.


Generally, a communication application establishes a communication session between transmitting and receiving terminals connected to each other through a network and performs communications on the established session. If a propagation delay time between the transmitting and receiving terminals is very long or they communicate with each other across networks having different properties such as wired and wireless networks, then the throughput of communications between the transmitting and receiving terminals is lowered.
One known method of solving the above problem has been not to perform communications between transmitting and receiving terminals on one session, but to install a relay device between transmitting and receiving terminals and relay data between two sessions, i.e., a session from the transmitting terminal to the relay device and a session from the relay device to the receiving terminal. Examples of such a session relay process include “Indirect TCP” described in Non-patent document 1 (Ajay Bakre and B. R. Badrinath “I-TCP; Indirect TCP for Mobile Host”, Department of Computer Science Rutgers University, DSC-TR-314, 1994) and communication methods described in Patent document 1 (Japanese patent No. 3448481), Patent document 2 (Japanese patent No. 3482091), and Patent document 3 (Japanese patent No. 3494610).
An example of session communications according to TCP will be described below. Details of an ordinary TCP process are described in Non-patent document 2 (Jon Postel, “Transmission Control Protocol”, IETF, RFC 793, 1981) and Non-patent document 3 (W. Richard Stevens, “TCP/IP Illustrated, Volume 1: The Protocols, Addison-Wesley”, 1994, ISBN 0-201-63346-989).
FIG. 1 shows a double-sided-transmission session relay device for relaying sessions transmissively from both a transmitting terminal and a receiving terminal. As shown in FIG. 1, double-sided-transmission session relay device 32-0 comprises packet input section 32-1 to which packets from a network are input, packet output section 32-2 which outputs packets to the network, session relay section 32-3 for terminating and relaying sessions, session status storing section 32-4 for storing a session status of session relay section 32-3, session determining section 32-5 for determining whether a packet is a session packet or not, session relay determining section 32-6 for determining whether a session relay process is to be performed or not, and session starting process monitoring section 32-7 for monitoring a session starting packet.
Packet input section 32-1 performs a process of receiving packets from the network. Session determining section 32-5 determines whether an input packet from packet input section 32-1 is a session packet or not. If the input packet is a session packet, then session determining section 32-5 passes the input packet to session relay determining section 32-6. If the input packet is a packet other than a session packet, then session determining section 32-5 passes the input packet to packet output section 32-2.
Session relay determining section 32-6 determines whether the session packet from session determining section 32-5 is a packet in a session registered in session status storing section 32-4 and also a packet sent after a session start acknowledging packet, or not. If these conditions are satisfied, then session relay determining section 32-6 passes the session packet from session determining section 32-5 to session relay section 32-3. If the conditions are not satisfied, then session relay determining section 32-6 passes the session packet from session determining section 32-5 to session starting process monitoring section 32-7.
When session starting process monitoring section 32-7 receives a session starting packet, it registers session information representing a reception sequence number (a sequence number to be received from a receiving terminal) and a transmission sequence number (a sequence number to be transmitted to a transmitting terminal) which are temporarily generated, but not yet determined. When session starting process monitoring section 32-7 receives a session start acknowledging packet, it determines the reception sequence number and the transmission sequence number, which have been temporarily generated, in the session information. After the processing of session starting process monitoring section 32-7 is over, the session packet from session determining section 32-5 is passed to packet output section 32-2.
Session relay section 32-3 performs a session relay process based on the session status stored in session status storing section 32-4, stores an updated session status in session status storing section 32-4, and passes a packet from session relay determining section 32-6 to packet output section 32-2, Packet output section 32-2 outputs the supplied packet to the network.
A session according to a TCP in the session relay device shown in FIG. 1 will be described below. In the session according to the TCP, a session starting packet and a session start acknowledging packet are referred to as a SYN packet and a SYN• ACK packet, respectively.
FIG. 2 is a block diagram of a network configuration including session relay device 32-0 shown in FIG. 1. FIG. 3 is a sequence diagram of a TCP relay process performed by session relay device 32-0 in the network configuration shown in FIG. 2. The example shown in FIG. 3 represents a sequence operation for transferring data from transmitting terminal 10 having IP address A to port number 80 of receiving terminal 20 having IP address B.
First, transmitting terminal 10 sends a connection starting SYN packet to receiving terminal 20. The connection starting SYN packet includes information representing source IP address “A”, source port number “x”, sequence number “1”, destination IP address “B”, and destination port number “80”.
In session relay device 32-0 on the route, the connection starting SYN packet from transmitting terminal 10 is supplied to packet input section 32-1. Packet input section 32-1 passes the supplied SYN packet to session determining section 32-5. Session determining section 32-5 determines that the packet from packet input section 32-1 is a session packet, and passes the packet to session relay determining section 32-6. Session relay determining section 32-6 determines that the packet received from session determining section 32-5 does not corresponds to a session registered in session status storing section 32-4, and passes the received packet to session starting process monitoring section 32-7.
Session starting process monitoring section 32-7 determines that the packet received from session relay determining section 32-6 is a session starting (SYN) packet, registers the session in session status storing section 1-4, and starts a session relay process to pass the received packet to packet output section 32-2. At this stage, at least a transmission sequence number to receiving terminal 20 and a reception sequence number from transmitting terminal 10 are stored in session status storing section 32-4. These two sequence numbers are initialized by the sequence number of the session starting (SYN) packet. The information of the session registered at this stage is incomplete session information as a whole because the transmission sequence number to receiving terminal 20 and the reception sequence number from transmitting terminal 10 have not yet been determined.
Having received the packet from session starting process monitoring section 32-7, packet output section 1-2 sends the received packet over the network to receiving terminal 20. The packet information in the SYN packet which is input to session relay device 32-0 and the packet information in the SYN packet which is output from session relay device 32-0 do not differ from each other.
When receiving terminal 20 receives the SYN packet from session relay device 32-0, it returns a SYN• ACK packet to transmitting terminal 10.
In session relay device 32-0 on the route, the SYN• ACK packet from receiving terminal 20 is supplied to packet input section 32-1. Packet input section 32-1 passes the SYN• ACK packet to session determining section 32-5. Session determining section 32-5 determines that the packet received from packet input section 32-1 is a session packet, and passes the received packet to session relay determining section 32-6. Session relay determining section 32-6 determines that the packet received from session determining section 32-5 corresponds to a session registered in session status storing section 1-4, and is not a packet after the session start acknowledging (SYN• ACK) packet, and passes the received packet to session starting process monitoring section 32-7.
Session starting process monitoring section 32-7 determines that the packet received from session relay determining section 32-6 is not a session starting (SYN) packet, but is a session start acknowledging (SYN• ACK) packet, updates the session information in session status storing section 32-4, and starts a session relay process to pass the received packet to packet output section 1-2. At this stage, the transmission sequence number to receiving terminal 20 and the reception sequence number from transmitting terminal 10 are updated. These two sequence numbers are initialized by the sequence number of the session start acknowledging (SYN• ACK) packet.
Having received the packet from session starting process monitoring section 32-7, packet output section 32-2 sends the received packet over the network to transmitting terminal 10. The packet information in the SYN• ACK packet which is input to session relay device 32-0 and the packet information in the SYN packet which is output from session relay device 32-0 do not differ from each other.
Thereafter, in session relay device 32-0, session relay section 32-3 returns an ACK packet responsive to the SYN• ACK packet to receiving terminal 20. In this manner, session relay device 32-0 opens a session between transmitting terminal 10 and receiving terminal 20.
When the communication route suffers a certain failure after the session has been opened, a status notification is performed according to ICMP (Internet control massage Protocol). Details of operation according to ICMP are described in Non-patent document 3 and Non-patent document 4 (Jon Postel, “INTERNET CONTROL MESSAGE PROTOCOL”, IETF, RFC 792, 1981).
If an IP header contains a “Don't Fragment” flag when the route includes zones of different MTUs (Maximum Transfer Units), then the data cannot be fragmented and transferred. One solution to this problem is a process called Path MTU discovery proposed in Non-patent document 5 (J. Mogul, S. Deering, “Path MTU discovery”, IETF, RFC 1191, 1990).
FIG. 4 shows a packet configuration of an ICMP Destination Unreachable/fragmentation request message. FIG. 5 shows a configuration of a PET part which has caused an error that is included in the ICMP Destination Unreachable/fragmentation request message. According to the Path MTU discovery process, if data cannot be fragmented and transferred because of the “Don't Fragment” flag in a router which includes zones of different MTUs, then the next-hop MTU is added to the ICMP Destination Unreachable/fragmentation request message shown in FIG. 4 and the message is sent to the source, so that the terminal of the source will retransfer a segment with a reduced MSS (Maximum Segment Size). In FIG. 4, “Internet Header+64 bits of Original Data Datagram” includes the information shown in FIG. 5 which is included in the packet which has caused the error.
When the communication route contains a plurality of zones of different MTUs, a process of notifying the source of an MTU according to the ICMP to reduce the MSS is repeated until a minimum MTU is detected. At the time the minimum MTU is detected, communications are made possible between the source and the destination. A similar process is disclosed in Patent document 4 (JP-A No. 2003-18216).
FIG. 6 is a diagram illustrative of an operation based on Path MTU discovery of a network apparatus having the double-sided-transmission session relay device shown in FIGS. 1 and 2. The operation based on Path MTU discovery with respect to an example according to TCP will be described below with reference to FIG. 6. In this example, the sum of IP and TCP header sizes is 40 bytes.
After the SYN process, transmitting terminal 421 (address: A, port: x) sends data having a segment size of 1460 bytes and a packet size of 1500 bytes toward receiving terminal 423 (address: B, part: 80). The data output from transmitting terminal 421 is supplied to router 422 (address: C). Since the next hop is in the zone of “MTU=500”, router 422 which has received the data from transmitting terminal 421 adds the next-hop MTU to the ICMP Destination Unreachable/fragmentation request message, and sends the message to transmitting terminal 421. The ICMP Destination Unreachable/fragmentation request message from router 422 is supplied to transmitting terminal 421.
In response to the fragmentation request message, transmitting terminal 421 resends data having a segment size of 460 bytes and a packet size of 500 bytes toward receiving terminal 423. As the packet size of the data resent from transmitting terminal 421 is 500 bytes, router 422 sends the data resent from transmitting terminal 421 to receiving terminal 423. As a result, the packet of the resent data reaches receiving terminal 423, allowing data to be exchanged continuously between transmitting terminal 421 and receiving terminal 423.


1. Field of the Invention
Embodiments of the invention generally relate to a traffic control device or marker (hereinafter collectively referred to as a “traffic control marker”). More particularly, various embodiments of the invention are directed to a traffic control marker having a mesh base and an improved inner core.
2. Description of the Related Art
Traffic control markers used on roadways or other marking areas are frequently struck by moving vehicles. These traffic control markers typically have an outer or primary tube mounted to a base. Typically, the traffic control marker includes a reflective sheeting partially or completely surrounding the primary tube to warn or guide an operator of the moving vehicle, for example, at night or through a construction zone. Examples of commonly used traffic control markers include traffic cones and barrels, as non-limiting examples.
Another type of traffic control marker is a flexible delineator highway marker. The highway marker typically includes a flexible insert positioned in a primary tube of the highway marker to provide it with a rebound effect. In particular, the insertion of the flexible insert into the primary tube of the highway marker allows the traffic control marker to return to a substantially upright position after being struck and deflected by a moving vehicle. In addition to other attachment methods, a conventional traffic control marker may be attached to the roadway using an epoxy or other adhesive.
A vehicular strike may overcome the seal created by the epoxy at the base of the traffic control marker, causing the traffic control marker to detach from the roadway at, or near, the base. Further, the primary tube, and thus the reflective sheet or indicia attached thereto, may detach from the traffic control marker upon impact by the moving vehicle. It can be costly and time consuming to repair or replace the damaged traffic control marker.
Thus, it would be desirable to provide a traffic control marker, or flexible highway marker, with an improved epoxy attachment mechanism capable of securing the primary tube to the base of the traffic control marker, thereby enhancing the structural integrity of the outer tube to prevent it from detaching from the traffic control marker on impact by a moving vehicle, improving the functioning life of the traffic control marker, and maintaining the performance of known types of flexible highway markers, when vehicles deflect them on the roadway or other marking area.


Fentanyl is a g-opioid receptor agonist with analgesic potency approximately 80-100 times that of morphine. In clinical settings, fentanyl exerts its principal pharmacologic effects on the central nervous system. Its primary actions are analgesic and sedation.
The analgesic effects of fentanyl are related to the blood level of the drug. In general, the minimum effective concentration and the concentration at which toxicity occurs rise with increasing tolerance to any and all opioids. The rate of development of tolerance may vary widely among individuals. All opioid mu-receptor agonists, including fentanyl, produce dose dependent respiratory depression. The risk of respiratory depression is typically less in patients receiving chronic opioid therapy who develop tolerance to respiratory depression and other opioid effects. Serious or fatal respiratory depression can occur, even at recommended doses, in vulnerable individuals.
Orally administered fentanyl is subject to first pass effect metabolism as upwards of 50% or more of orally administered fentanyl is not absorbed. Other forms of delivery such a parenteral, buccal, and transdermal have been utilized to decrease or avoid this first pass effect for fentanyl.
Fentanyl is currently available in injectable form, as a lozenge (e.g. Actiq® fentanyl citrate; Actiq is a registered trademark of Anesta, LLC), and as a transdermal patch (e.g. Duragesic® 25, 50, 75, and 100 μg of fentanyl per hour; Duragesic is a registered trademark of Johnson & Johnson Corporation). Duragesic® provides continuous systemic delivery of fentanyl for approximately 72 hours. Duragesic® is indicated in the management of chronic pain in patients requiring continuous opioid analgesia for pain that is not optimally managed with lesser means such as acetaminophen-opioid combinations, non-steroidal analgesics, or prn (as needed) dosing with short-acting opioids. Duragesic® is typically not suitable for patients experiencing acute pain due to the delay in absorption of the fentanyl through the patch, or postoperative pain because serious or life-threatening hypoventilation could result.
Actiq® is a solid formulation of fentanyl citrate, intended for oral transmucosal administration. Actiq® is a lozenge attached to a handle similar in shape to a lollipop. The handle is purportedly to allow the Actiq® unit to be removed from the mouth if signs of excessive opioid effects appear during administration. Actiq® is indicated for the management for breakthrough cancer pain in patients with malignancies who are already receiving and who are tolerant to opioid therapy for their underlying persistent cancer pain. Actiq® is contraindicated in the management of acute or postoperative pain.
Sublingual tablets and lozenges (e.g., Actiq®) which may be used for acute pain or breakthrough pain have certain disadvantages. A disadvantage, amongst others, is that after intake the active agent in these pharmaceutical agents must first be released and dispersed prior to being available for resorption in dissolved form. In addition, the absorption pharmacokinetics of fentanyl from Actiq® may vary depending on the fraction of the dose that is absorbed through the oral mucosa and the fraction swallowed. Further, certain lozenges may be in the form of a candy which require medical supervision and may be socially questionable.
There exists a need in art for a sublingual formulation including fentanyl, a pharmaceutically acceptable salt thereof, or derivative thereof, which is suitable for effective pain management.


1. Field of the Invention
The present invention relates to a viewfinder brightness control circuit for a camcorder. More specifically, the present invention relates to a circuit which automatically controls the brightness of the image produced by an electronic viewfinder by applying an iris output voltage, which voltage varies in response to the sensed illumination of the environment.
2. Discussion of Related Art
When an object is photographed by a camcorder, the image quality produced by the electronic viewfinder is greatly affected by the illumination, i.e., the brightness of the surrounding. Accordingly, when an object is photographed by the camcorder, the viewfinder needs to be adjusted to compensate for the ambient illumination so that the image quality at the viewfinder is acceptable.
As shown in FIG. 3, a camcorder 100 includes a lens group 102 directing light through an iris 104 to a target 108. It will be appreciated that target 108 can be, e.g., a charge-coupled device (CCD) or similar device. Signals produced by target 108 are provided to a video signal processor 112 via a preamp 110. An indication of the brightness level at the target is provided from processor 112 to an iris motor 106, which is connected to iris 104, via an amplifier 114. Additionally, the video signal produced by video signal processor 112 is provided to an electronic viewfinder (EVF) 118 via control circuitry 116. In an exemplary case, the control circuitry included in block 116 is as shown in FIG. 1.
In general, brightness at the viewfinder is designed to be manually controlled. As shown in FIG. 1, a conventional viewfinder brightness control circuit includes an amplifier 1 and a light controller 3.
Amplifier 1 includes a PNP transistor Q1 whose base is connected to a video signal input terminal via capacitor C1, whose emitter is grounded via a resistor R4, and whose collector is connected to a power voltage (Vcc) input terminal via a resistor R3; a resistor R1 connected between the power voltage input terminal and the base of PNP transistor Q1; a resistor R2 connected between the base of PNP transistor Q1 and ground; and a capacitor C2 having one terminal connected to the collector of PNP transistor Q1 and the other terminal connected to EVF 118 via light controller 3.
Light controller 3 includes a resistor R5 connected between the other terminal of capacitor C2 (hereinafter node A) and the power voltage input terminal, a variable resistance VR1 and a resistor R6 connected to ground via the common node of capacitor C2 and resistor R5, and a capacitor C3 connected between the wiper of variable resistor VR1 and ground. It will be noted that the wiper of variable resistor VR1 is also connected to node A between capacitor C2 and resistor R5.
Voltage at node A varies depending on variable resistor VR1 in light controller 3 and the video signal level output to the EVF 118 is determined in accordance with the variation in node A voltage. Thus, electronic viewfinder brightness is controlled by a video signal level output to EVF 118. In other words, if the viewfinder is located in well illuminated area, the voltage level of the video signal output to the electronic viewfinder will be high. When the electronic viewfinder is located in a poorly illuminated area, the voltage level of a video signal output to a viewfinder will be low. Accordingly, viewfinder brightness can be adjusted by controlling the resistance value of variable resistor VR1. It will be noted that the resistance value has to be selected in response to voltage level corresponding to the brightness level such that the voltage level is controlled after the user confirms the viewfinder brightness.
As described above, in the conventional operating method, the user directly controls variable resistor VR1 attached to the camcorder in order to control electronic viewfinder brightness. When the user operates the camcorder without manually adjusting the variable resistor, e.g., if the user depends on a preset brightness value stored in the camcorder, or when brightness is controlled after a video signal is displayed on the electronic viewfinder, the resolution of a viewfinder image quality can be deteriorated. This is a source of great inconvenience to a camcorder user.


This invention relates to a mixing element for mixing two or more fluids and a motionless mixer using the same.
Motionless mixers (trademark: Static Mixers) have no mechanical moving parts and are so designed that fluids are mixed as they are passed through passages in a tube having a helical blade therein. The motionless mixers of this type are used in various fields, such as chemical plants, food industry, environmental pollution prevention technology, etc. In a prior art motionless mixer, as shown in FIGS. 1 to 3, a plurality of helical blades 1 and 2 formed by twisting sheets left- or right-handed respectively at an angle of 180 degrees are arranged in a passage tube 3. The blades 1 and 2 are coupled and fixed so that the facing end edges of each two adjacent blades cross at right angles. Two fluids flow individually through regions in the passage tube 3 partitioned by the blades 1 or 2, and are divided and joined at the junction of the blades. Then, the fluids flow helically, and are divided and joined at the next junction. After such division, joining, and transfer are repeated, the two fluids are mixed thoroughly.
Conventionally, the helical blades 1 and 2 are manufactured by casting, and each two helical blades 1 and 2 are fixedly coupled by welding or brazing so that their facing end edges cross at right angles. Helical blades fixedly coupled are inserted into the hollow cylindrical passage tube 3. Thus, the manufacture of the motionless mixer is not easy, and the fluids may often stagnate at the junctions where the adhesive agent is swollen. Owing to working errors, moreover, narrow gaps are formed between the helical blades 1 or 2 and the passage tube 3. These gaps reduce the efficiency of fluid mixing. As shown in the sectional view of FIG. 4 taken along line IV--IV of FIG. 3, the surface of the blade 1 and the inner peripheral surface of the passage tube 3 cross at substantially right angles, so that acute-angled dead spaces 4 are formed at four corner portions of the inside regions of the passage tube 3 partitioned by the blade 1. The fluids may stagnate at the dead spaces 4. Moreover, the flatness of an end edge 1a of the blade 1 increases the flow resistance.
FIG. 5 shows a motionless mixer with helically twisted fluid passage tubes. As shown in FIG. 6, the fluid passage of each of passage tubes 5a and 5b has a semicircular cross section. The pair of passage tubes 5a and 5b are twisted helically, and are coupled so that their boundary between passage tubes 5a and 5b crosses the boundary between their adjacent pair of similar passage tubes 6a and 6b at right angles at the longitudinal end portions. Since it is difficult to manufacture a pair of helically twisted tubes, the manufacturing cost of this motionless mixer is high.


The present invention generally relates to ignition systems for gasoline engines. More particularly, the invention relates to a discharge ignition apparatus having triggering circuitry that generates a triggering signal based upon stored timing data.
Ignition circuits of relatively elaborate design have often been provided to advance the ignition spark as engine speed is increased. For example, the spark may be delayed at starting speeds until approximately peak compression of the engine""s piston. At higher engine speeds, the spark is preferably advanced to occur before peak compression.
U.S. Pat. No. 5,392,753 to Burson et al., incorporated herein by reference, shows an ignition circuit utilizing a microprocessor.
In one aspect, the present invention provides an ignition apparatus for use with an internal combustion engine to produce an electrical spark at a spark ignition device. The apparatus comprises a magnet assembly, including a pair of pole faces, operatively revolved along a circular path. A magnetically permeable core is mounted adjacent to the circular path and has at least two leg portions each including a respective end face. The leg portions of the magnetically permeable core are situated such that the pole faces pass proximate to the end faces during revolution of the magnet assembly. As a result, a time-varying magnetic flux is produced in the magnetically permeable core.
The ignition apparatus further includes a transformer having a primary coil and a secondary coil related by a predetermined step-up ratio. The secondary coil is electrically connected during operation to the spark ignition device. A spark generation circuit is operative to apply a primary voltage pulse to the primary coil responsive to a triggering signal. The primary voltage pulse produces a spark generating pulse in the secondary coil.
In addition, the ignition apparatus includes triggering circuitry having a processor with stored timing data. The processor is operative to receive a signal indicative of the rotational position of the magnet assembly and produce a triggering signal. In a first mode, the triggering signal occurs at a fixed angle relative to top dead center. In a second mode, the triggering signal occurs at a variable angle relative to top dead center based on the stored timing data.
Other objects, features and aspects of the present invention are discussed in greater detail below.


Reliable and consistent statistics relating to network traffic flow are important diagnostic tools in the operation of the modern datacenter. For instance, several classes of network errors and even failures include forwarding errors, very low rate packet loss that isn't accounted for by the device that is actually losing the packet, which may be identified if accurate packets statistics are available. However, current packet (and/or byte) counting methodologies and/or devices often fail to provide an accurate and consistent assessment of packet flow across a network, which negatively impacts the ability of this type of statistical information to serve the desired diagnostic purposes.


Prior attempts to provide information technology (IT) system coverage information, and IT management system information focus on management and coverage systems that stand alone. Each system has its own method of figuring out which resources it manages. Lists of resources generated by such systems may be incomplete, as each system is not aware of resources they do not manage. In recent years there has been an increase in the number of policies with which to comply. Compliance with the policies is only being checked for resources each system is aware of, creating the risk that a resource unknown to a system will create a noncompliance issue.


1. Field of the Invention
The present invention relates generally to improvements in portable spas, and more particularly, pertains to new and improved water features for a portable spa wherein a waterfall is provided as part of the portable spa for the enjoyment and entertainment of the spa users.
2. Description of Related Art
In the field of portable spas, manufacturers are continually trying to enhance the portable spa product by adding various entertainment features to it beyond the hot water and jet massaging functions. Manufacturers have added audio systems to a portable spa device. Some manufacturers have added water features, such as waterfalls, to portable spa devices. The problem associated with the inclusion of a waterfall in a portable spa is the amount of space required by the waterfall. The present invention overcomes this problem.


In a typical communications network a wireless device, communicates via a Radio Access Network (RAN) to one or more Core Networks (CNs). The communications network may also be referred to as e.g. a wireless communications network, a wireless communications system, a communications network, a communications system, a network or a system.
The wireless device may be a device by which a subscriber may access services offered by an operator's network and services outside operator's network to which the operator's radio access network and core network provide access, e.g. access to the Internet. The wireless device may be any device, mobile or stationary, enabled to communicate over a radio channel in the communications network, for instance but not limited to e.g. user equipment, mobile phone, smart phone, sensors, meters, vehicles, household appliances, medical appliances, media players, cameras, Machine to Machine (M2M) device or any type of consumer electronic, for instance but not limited to television, radio, lighting arrangements, tablet computer, laptop or Personal Computer (PC). The wireless device may be portable, pocket storable, hand held, computer comprised, or vehicle mounted devices, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another wireless device or a server.
The radio access network covers a geographical area which is divided into cell areas, with each cell area being served by a base station. The base station may be called a Radio Base Station (RBS), evolved NodeB (eNB), NodeB, B node, Radio Network Controller (RNC), Base Station Controller (BSC), Base Transceiver Station (BTS), MCE, depending on the technology and terminology used. A cell is a geographical area where radio coverage is provided by the radio base station at a base station site. The base station communicates with the wireless device(s) within range of the base station.
According to the 3GPP, Multimedia Broadcast Multicast Services (MBMS) “is a point-to-multipoint service in which data is transmitted from a single source entity to multiple recipients. Transmitting the same data to multiple recipients allows network resources to be shared.” MBMS offers two modes: broadcast mode and multicast mode. The MBMS architecture enables efficient usage of radio network and core network resources. evolved MBMS (eMBMS) may be described as the Evolved Packet Core (EPC) version of MBMS. The eMBMS evolution brings improved performance thanks to higher and more flexible LTE bit rates, single frequency network operations, and carrier configuration flexibility.
In MBMS, there are some network nodes or functional entities which are important. Multi-cell/multicast Coordination Entity (MCE) is a network node or functional entity which is responsible for allocation of time and frequency resources for MBMS transmission. The MCE may be co-loated with for example an eNB. Another network node is the MBMS-GW, which is the entry point for incoming broadcast/multicast data traffic. The MBMS-GW broadcasts data packets to all eNBs within an area. Broadcast Multicast-Service Centre (BM-SC) is a network node or functional entity which is necessary in order for a communications network to support MBMS. The BM-SC is in charge of providing service to the end user.
Some of the reference points in MBMS are Sn, SGmb and Sm. Sn is the reference point for the control plane between MBMS-GW and the SGSN. SGmb is the reference point for the control plane between BM-SC and the MBMS-GW. Sm is the reference point for the control plane between the Mobility Management Entity (MME) and the MBMS-GW. M3 Application Protocol (M3AP) supports the M3 interface which is between the MCE and the MBMS GW. A reference point may also be referred to as an interface. Signaling between nodes is exchanged at a reference point.
The purpose of a MBMS Session Start procedure is to request the radio access network to notify wireless devices about an upcoming MBMS Session of a given MBMS Bearer Service and to establish a MBMS Radio Access Bearer (RAB) and MBMS signalling connection for this MBMS Session. The MBMS Session Start procedure is triggered by the core network. For example, the core network initiates the procedure by sending a MBMS Session Start request message to the RNC. The MBMS Session Start request message comprises different parameters. The RNC acts according to the received MBMS Session Start request message. The RNC sends a MBMS Session Start response message or a MBMS Session Start failure message to the core network, depending on the outcome of the procedure.
According to 3GPP, the loss or corruption of the data stored in the aforementioned network entities for support of MBMS service(s) for each MBMS session context which are created by the MBMS Session Start procedure and updated by the MBMS Session Update procedure will seriously degrade the MBMS service(s) offered to mobile subscribers. It is therefore necessary to define procedures to limit the effects of such failure, and to restore the MBMS service with minimized impact to the mobile subscribers. Such restoration procedures are related to failure and/or restart of several types of network nodes and network paths/interfaces, such as e.g. MBMS-GW, MME, SGSN etc. The terms restoration and re-establishment are equivalent.
A failure may be a failure to receive a particular message, failure of a hardware or software component of a network node. A failure may be full/complete or partial. After a node has been restarted, all its bearer contexts are deleted.
3GPP has started a new project called eMBMS restoration procedures, where the objective of this project is to specify enhanced restoration procedures to explicitly define the EPS behavior and to enable restoration of the eMBMS service when possible in order to minimize the end-user service impact upon different kinds of failure over the control path. Examples of such failures are as follows:                MBMS-GW failure/restart        MME/SGSN failure/restart        MCE failure/restart        BM-SC failure/restart        Sm/Sn path failure        M3AP path failure        SGmb path failure
It has been agreed that the principle of these restoration procedures is to try to re-establish the control path to allow a subsequent MBMS session update and/or MBMS session stop. In addition, such re-establishing may be performed before bringing down the MBMS sessions. But the specific procedures under various failure scenarios are still under discussion.
The system behaviour upon restoration of a MBMS session towards an alternative downstream node during a SGmb path failure remains undefined in current standards.


The present invention involves the ejection of ink drops by way of forming gas or vapor bubbles in a bubble forming liquid. This principle is generally described in U.S. Pat. No. 3,747,120 to Stemme. These devices have heater elements in thermal contact with ink that is disposed adjacent the nozzles, for heating the ink thereby forming gas bubbles in the ink. The gas bubbles generate pressures in the ink causing ink drops to be ejected through the nozzles.
The resistive heaters operate in an extremely harsh environment. They must heat and cool in rapid succession to form bubbles in the ejectable liquid, usually a water soluble ink. These conditions are highly conducive to the oxidation and corrosion of the heater material.
Dissolved oxygen in the ink can attack the heater surface and oxidise the heater material. In extreme circumstances, the heaters ‘burn out’ whereby complete oxidation of parts of the heater breaks the heating circuit.
The heater can also be eroded by ‘cavitation’ caused by the severe hydraulic forces associated with the surface tension of a collapsing bubble.
To protect against the effects of oxidation, corrosion and cavitation on the heater material, inkjet manufacturers use stacked protective layers, typically made from Si3N4, SiC and Ta. Because of the severe operating conditions, the protective layers need to be relatively thick. U.S. Pat. No. 6,786,575 to Anderson et al (assigned to Lexmark) is an example of this structure, and the heater material is ˜0.1 μm thick while the total thickness of the protective layers is at least 0.7 μm.
To form a vapor bubble in the bubble forming liquid, the heater (i.e. the heater material and the protective coatings) must be heated to the superheat limit of the liquid (˜300° C. for water). This requires a large amount of energy to be supplied to the heater. However, only a portion of this energy is used to vaporize ink. Most of the ‘excess’ energy must be dissipated by the printhead and or a cooling system. The heat from the excess energy of successive droplet ejections can not raise the steady state temperature of the ink above its boiling point and thereby cause unintentional bubbles. This limits the density of the nozzles on the printhead, the nozzle firing rate and usually necessitates an active cooling system. This in turn has an impact on the print resolution, the printhead size, the print speed and the manufacturing costs.
Attempts to increase nozzle density and firing rate are hindered by limitations on thermal conduction out of the printhead integrated circuit (chip), which is currently the primary cooling mechanism of printheads on the market. Existing printheads on the market require a large heat sink to dissipate heat absorbed from the printhead IC.
Inkjet printheads can also suffer from a problem commonly referred to as ‘decap’. This term is defined below. During periods of inactivity, evaporation of the volatile component of the bubble forming liquid will occur at the liquid-air interface in the nozzle. This will decrease the concentration of the volatile component in the liquid near the heater and increase the viscosity of the liquid in the chamber. The decrease in concentration of the volatile component will result in the production of less vapor in the bubble, so the bubble impulse (pressure integrated over area and time) will be reduced: this will decrease the momentum of ink forced through the nozzle and the likelihood of drop break-off. The increase in viscosity will also decrease the momentum of ink forced through the nozzle and increase the critical wavelength for the Rayleigh Taylor instability governing drop break-off, decreasing the likelihood of drop break-off. If the nozzle is left idle for too long, these phenomena will result in a “decapped nozzle” i.e. a nozzle that is unable to eject the liquid in the chamber. The “decap time” refers to the maximum time a nozzle can remain unfired before evaporation will decap the nozzle.


1. Field of the Invention
The present invention relates to a method for the production of high purity calcium thiosulfate by a metathesis reaction of ammonium thiosulfate and calcium hydroxide or calcium oxide.
2. Description of the Prior Art
Although the prior art contains many references to the production of calcium thiosulfate, at present, there are no known commercial processes for the manufacture of high purity calcium thiosulfate.
Japanese Pat. No. 6,039, issued Feb. 22, 1973, discloses a process for the manufacture of calcium or magnesium thiosulfate by reacting calcium or magnesium sulfite with sulfur in alkaline solution. High yields are obtained only in the preparation of magnesium thiosulfate. This Japanese patent also discloses a metathesis reaction between calcium hydroxide and magnesium thiosulfate to produce calcium thiosulfate and insoluble magnesium hydroxide. However, the preparation of calcium thiosulfate solutions according to this Japanese patent requires a difficult filtration of a slurry containing magnesium hydroxide.
In Spanish Pat. 245,171, issued Nov. 15, 1958, a process is disclosed for the preparation of calcium thiosulfate by reacting a mixture of calcium chloride hexahydrate and calcium hydroxide with a concentrated solution of sodium thiosulfate at 30.degree. C. Not only are 0.77 tons of co-product sodium chloride produced for every ton of calcium thiosulfate produced but residual sodium chloride is an objectionable contaminant, e.g., when calcium thiosulfate is used as a non-corrosive hardening accelerator for concrete.
High purity calcium thiosulfate hexahydrate (CaS.sub.2 O.sub.3.6H.sub.2 O) is produced by a metathesis reaction between a concentrated solution of calcium chloride hexahydrate and sodium thiosulfate pentahydrate, described in Monatsh, 80, 220-31 (1949). A stream of nitrogen is bubbled into the reaction mixture to exclude air and CO.sub.2 and the pH of the metathesis reaction solution is adjusted to about 8 to 9 by addition thereto of calcium oxide. However, the solid calcium thiosulfate so produced requires a purification step at temperatures of 0.degree. C or lower.
It is accordingly an object of the present invention to provide a method for the production of high purity calcium thiosulfate by a metathesis reaction wherein difficult processing steps and objectionable impurities are avoided and conversion rates are high.
It is another objection of the present invention to provide a process for the production of aqueous solutions of high purity calcium thiosulfate up to the saturation concentration under conditions which minimize the decomposition of the thiosulfate ion.
It is still further an object of the present invention to provide a method for the production of calcium thiosulfate wherein integration of said method with a process for the manufacture of the ammonium thiosulfate feedstock is feasible.
Other objects and advantages of the present invention will become apparent from the description which follows.


1. Field of the Invention
This invention generally relates to telecommunications and, more particularly, to maintenance termination units for locating trouble in a telecommunications network.
2. Description of the Related Art
Maintenance termination units help locate trouble in a telecommunications network. When trouble is reported, that trouble may lie within the customer's premises and/or within the local loop serving the customer. Maintenance termination units have been used to help determine whether the trouble lies within the local loop or within the customer's premises.
U.S. Pat. No. 4,529,847 to DeBalko (issued Jul. 16, 1985) shows a maintenance termination unit. This maintenance termination unit comprises a pair of “normally open” voltage switches connected between the ring and tip of the local loop (see Column 3, lines 30–33). When this maintenance termination unit is installed at the customer's premises, the maintenance termination unit produces a distinctive, periodic DC signal (see Column 4, lines 37–50). When a fault lies within the customer's premises, this distinctive, periodic DC signal is produced regardless of polarity between the ring and the tip (see Column 4, line 63–Column 5, line 1). If trouble lies within the telecommunications network, then the maintenance termination unit produces either a steady signal (a “hard” fault) or a periodic signal (a “light” fault) (see Column 5, lines 1–7). Because this maintenance termination unit utilizes voltage switches, these switches unfortunately cycle between an open position and a closed position when indicating the presence of a fault (see Column 4, lines 46–48). This periodic signal is often confused by test technicians and leads to an inaccurate diagnosis. This constant cycling, between an open position and a closed position, also leaves little time to conduct a test of the local loop.
Other maintenance termination units have disadvantages. Many of these prior art maintenance termination units utilize custom, integrated circuitry. These integrated circuits are expensive and time-consuming to design and to fabricate. The expense of designing and fabricating these circuits, in fact, is often cost-prohibitive. Even when an integrated circuit is used, the harsh, ambient environment leads to many field failures. When the integrated circuit fails, the entire maintenance termination unit is then wastefully discarded.
There is, accordingly, a need for an improved maintenance termination unit that is easier to use, less expensive to design and to manufacture, tolerant of ambient conditions, and cheaper to repair or replace in the field.