Let's first begin by setting our discussion in the proper context. Bandwidth can refer to many things depending upon the application being discussed. When it comes to radio, bandwidth often refers to wave length. In optics it is the width of an individual spectral line or the entire spectral range. For our discussion, we will be speaking of bandwidth in terms of digital communication.
Even here the term can be misleading. We will use the term as it is most commonly referred to in reference to the internet. That is as a unit of measurement that represents the rate at which data or bits of information may be transmitted through a system.
Think of bandwidth as a pipe or a hose. The bigger the pipe or hose, the larger the volume of water that you can put through it. Do not confuse this with pressure. By constricting a pipe, one can cause water to be expelled very rapidly. However, did more volume of water actually flow through the pipe? Now apply the same concept to telecommunications. Bandwidth is the pipe or hose of the communications industry. The larger the pipe, the more information that can be passed through it. Assume that there is a small campfire. If we have a regular garden hose, we should be able to get enough volume of water through it to put the fire out. Now imagine your house is on fire. Your little garden hose won't be of much help in this instance. You need a large diameter hose such as that used by your local fire department. Even more importantly, they don't come and hook their hoses up to your outside spigot do they? No, they use the large pipes connected to the local fire hydrant.
Now let's get back to our garden hose of telecommunications. This is actually a regulated flow, with a number of control mechanisms.
First there is the diameter of the water pipe. It only allows a certain amount to flow through it. There is the hose itself. This is usually even smaller in diameter, so flow is restricted even more.
The spigot acts as the final control mechanism. You can open or close the spigot to increase or decrease the desired flow.
What are the purposes of these constraints? To help control the flow of water through the system. Enough is let through to meet our needs. If more were allowed to flow through, we may experience flooding or over saturation. The control mechanisms help to avoid waste.
Now imagine our house fire situation again. Even opened up to it's fullest, the garden hose can not allow enough volume through it to put out the fire. A larger hose and pipe are needed to get adequate flow to do the job.
Bandwidth is similar to this. Bandwidth is the range of frequencies that can be carried across a given transmission channel. The more information being sent, the more bandwidth is necessary. A typical analog telephone line requires 3-khz to handle voice communications. The phone company actually breaks the electromagnetic spectrum into 4-khz slices. These slices are limited with bandpass filters (think spigot). Now this works well until we introduce data into the equation. At that point there is not enough capacity in the typical phone line to handle the additional information that must be moved through the system.
These services are can be likened to the fire companies’ hoses and the fire hydrant. They are Broadband Services. In telecommunications, broadband refers to a system capable of carrying a relatively wide range of frequencies. These frequencies can then be divided into channels. Each channel can then be used to transmit information. The more frequencies or channels, the more information can be transmitted. In other words, more frequencies equals a bigger hose. This hose then connects to the central office of the telephone company or a bigger spigot, much like the fire hydrant. This is why most companies are moving away from the typical dial-up service and into either DSL, Cable Modem, Satellite or T1 service. They are simply looking for a bigger hose to put more information through in order to satisfy and extinguish the ever present demand (fire) for more information.
Scott Pimental is an independent telecommunications consultant who specializes in working with small to medium sized businesses to meet their telecommunications needs. You can find additional information, resources and services focused on broadband, telephone and Voice Over Internet Protocol (VOIP) by visiting his sight at http://www.amtecdigital.com