Communications The electronic transfer of information from one location to another. "Data communications" or "datacom" refers to digital transmission, and "telecommunications" or "telecom" refers to a mix of voice and data, both analog and digital. "Networking" refers specifically to LANs and WANs. The term "communications" used by itself generally pertains to telecom-related subjects such as PBXs, modems, call centers and the like. However, the word is also a generic English word that is used descriptively such as in the headline "Analog Vs. Digital Communications" below. Thus, "communications" is used specifically in some cases and more generically in others. The Protocol The way data communications systems "talk to" each other is defined in a set of standards called "protocols." Protocols work in a hierarchy starting at the top with the user's program and ending at the bottom with the plugs, sockets and electrical signals. See communications protocol and OSI. Analog Vs. Digital Communications The world's largest communications system is the telephone network, which is a mix of analog and digital communications. The system, which used to be entirely analog and transmitted only voice frequencies is now almost entirely digital. The only analog part is the line between your telephone and a digital conversion point (digital loop carrier) within a mile or so of your house. Analog systems are error prone, because the electronic frequencies get mixed together with unwanted signals (noise) that are nearby. In analog telephone networks, amplifiers were placed in the line every few miles to boost the signal, but they could not distinguish between signal and noise. Thus, the noise was amplified along with the signal. By the time the receiving person or machine got the signal, it may have been impossible to decipher. In a "digital" network, only two (binary) distinct frequencies or voltages are transmitted. Instead of amplifiers, repeaters are used, which analyze the incoming signal and regenerate a new outgoing signal. Any noise on the line is filtered out at the next repeater. When data are made up of only two signals (0 and 1), they can be more easily distinguished from the garble. Digital is simple!
Information - Information is a term with many meanings depending on context, but is as a rule closely related to such concepts as meaning, knowledge, instruction, communication, representation, and mental stimulus. Although many people speak of the advent of the "information age," the "information society," and information technologies, and even though information science and computer science are often in the spotlight, the word "information" is often used without careful consideration of the various meanings it has come to acquire. Often information is viewed as a type of input to an organism or designed device. Inputs are of two kinds. Some inputs are important to the function of the organism (for example, food) or device (energy) by themselves. In his book Sensory Ecology, Dusenbery called these causal inputs. Other inputs (information) are important only because they are associated with causal inputs and can be used to predict the occurrence of a causal input at a later time (and perhaps another place). Some information is important because of association with other information but eventually there must be a connection to a causal input. In practice, information is usually carried by weak stimuli that must be detected by specialized sensory systems and amplified by energy inputs before they can be functional to the organism or device. For example, light is often a causal input to plants but provides information to animals. The colored light reflected from a flower is too weak to do much photosynthetic work but the visual system of the bee detects it and the bee's nervous system uses the information to guide the bee to the flower, where the bee often finds nectar or pollen, which are causal inputs, serving a nutritional function. The most important meanings of information are identified in the following sections roughly in order of narrowest to broadest.
Information as a message: Information is a message, something to be communicated from the sender to the receiver, as opposed to noise, which is something that inhibits the flow of communication or creates misunderstanding. If information is viewed merely as a message, it does not have to be accurate. It may be a lie, or just a sound of a kiss. This model assumes a sender and a receiver, and does not attach any significance to the idea that information is something that can be extracted from an environment, e.g., through observation or measurement. Information in this sense is simply any message the sender chooses to create.
Telephone, device for communicating sound, especially speech, usually by means of wires in an electric circuit. The telephones now in general use evolved from the device invented by Alexander Graham Bell and patented by him in 1876 and 1877. Although Bell is recognized as the inventor, his telephone was preceded by many attempts to produce such an instrument. The principles on which it is based, and effective model instruments, were developed by different men at so nearly the same time that there are disputes about priority. In Bell's instrument, an electric current varied in intensity and frequency in accordance with sound waves. The sound waves caused a thin plate of soft iron, called the diaphragm, to vibrate. The vibrations disturbed the magnetic field of a bar magnet placed near the diaphragm, and this disturbance induced an electric current in a wire wound about the magnet. That current, when transmitted to a distant identical instrument, caused the diaphragm in it to vibrate, reproducing the original sound. Bell's instrument was thus both transmitter and receiver. The first notable improvement of the Bell telephone differentiated the transmitting instrument from the receiving instrument. Many other inventions have improved the telephone.
The switches used to route telephone calls, which were once electromechanical, are now largely replaced by sophisticated digital electronic switching systems. The electronic switches are much more flexible because they can be programmed to provide new services. The latest generation of switches have made a number of new features possible. Users, for example, can read the telephone number of the calling party on a display device if they choose to subscribe to a "caller ID" service. In "call waiting," audio signals let a person already on a telephone know that someone else is trying to reach that person. Subscribers can also program the telephone switches to forward their calls automatically to another number ("call forwarding"). Other features include voice mailboxes and the ability to make three-way conference calls.
The problems associated with long-distance and intercity telephone service have been met with increasing success. The telephone lines used include the ordinary open wire lines, lead-sheathed cables consisting of many lines, and coaxial and fiber-optic cables. Coaxial and fiber-optic cables are typically placed underground, but other cables may be either overhead or underground. Transmission of telephone messages over long distances is often accomplished by means of radio and microwave transmissions. In some cases microwaves are sent to an orbiting communications satellite (see satellite, artificial) from which they are relayed back to a distant point on the earth. Cellular telephone systems allow small, low-power portable radio transceivers access to the telephone network; some cellular models provide access to the Internet.
The incorporation of microelectronics and digital technology has led to the inclusion of unrelated applications in telephones, such as alarm clocks, calculators, and voice memos for recording short verbal reminders. A camera phone is a cellular phone that has photo taking and sending (to another camera phone or computer) capability. Similarly, a videophone transmits and receives real-time video images.
With the advent of the Internet, computer programs have been developed that allow voice communications across long distances, bypassing conventional carriers. The programs, which often require a computer equipped with a telephone or cable modem, microphone, and speakers, compress the voice message into digital signals. In other cases, a special adapter is used to allow a standard telephone to access the Internet directly though a cable modem or other broadband connection, or an Internet telephone (IP phone) may be used instead. The digital signals may be transmitted over the Internet to another computer, which must have another copy of the same program, or to a telephone. If a connection is established with another computer, the second program decompresses the digital signals and plays the sound almost instantaneously. The advantage of using the Internet is that under current tariffs no long-distance charges accrue on a computer to computer call, regardless of the length of the conversation. The disadvantages are the inferior sound quality on dialup connections and, in some cases, the need to have computers that are running the same program and the need to establish a connection between those computers.
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