Most of you know what cable TV is. Many of you have it. Those of you who don't wish that you did. Cable TV is enhanced over regular television because it provides more channels and clearer pictures.

Sometimes, cable companies offer Internet access over your TV cables! This is possible because the cable has such a high bandwidth that TV channels only take up a fraction of it. In case you don't know, bandwidth is a term used to measure how much data a cable or wire can transfer per second. A cable modem gives downstream data (data going from the Internet to your home computer) a 6-megahertz (MHz-megahertz is merely a measurement of frequency that means something makes one million cycles per second) channel in the cable. Meanwhile, upstream data (data going from your home computer to the Internet) is given a 2-megahertz channel. Upstream data is given less bandwidth because most people download stuff from the Internet more than they upload.

There are 5 major parts of a cable modem:

1. Tuner
The tuner is a device that connects to the outlet of the CATV. CATV is an acronym for Cable TV system. The tuner receives a digital signal from the modulator and then passes this on to the demodulator.

2. Demodulator

Demodulators usually contain a quadrature amplitude modulation (QAM). You can imagine analog signals as looking like sine and cosine graphs. For those of you who haven't studied trigonometry yet, the sine and cosine graphs look like little curves. QAM takes these analog signals and encodes information in them by varying their amplitudes and their phases (i.e. how tall the graph is, etc.). Then, this signal goes through the A/D converter, where it is turned into digital form-a series of 0s and 1s. The demodulator also consists of an error correction unit that checks for errors, as well as a MPEG frame synchronizer that makes sure groups of data stay together and in order.

3. Modulator

The modulator in cable modems is often called a burst modulator. This is used to convert digital information into a series of analog signals. They contain a QAM, like demodulators. However, instead of having an A/D converter, modulators have a D/A converter. This converts the information from digital form to analog form. Finally, the modulator, like the demodulator, contains an error correction module to check for errors.

4. MAC

The Media Access Control mechanism, or MAC, sits between the upstream and downstream paths. They act as an interface between hardware and software portions of the networks. Usually, they often need the help of the cable modem's central processing unit to carry out all of their responsibilities.

5. CPU

The microprocessor of a cable modem has various functions. Usually, they are used to help perform some of the MAC's duties. They also perform processing tasks.