Modems :: essays research papers

Modems Modems are used to connect two computers over a phone line. Modem is short for Modulator Demodulator. It's a device that converts data from digital computer signals to analog signals that can be sent over a phone line. This is called modulation. The analog signals are then converted back into digital data by the receiving modem. This is called demodulation. A modem is fed digital information, in the form of ones and zeros, from the CPU. The modem then analyzes this information and converts it to analog signals, that can be sent over a phone line. Another modem then receives these signals, converts them back into digital data, and sends the data to the receiving CPU. At connection time, modems send tones to each other to negotiate the fastest mutually supported modulation method that will work over whatever quality line has been established for that call. There are two main differences in the types of modems for PC, internal and external modems. Evolution of Modems In the last 10 years, modem users have gone from data transfer rates of 300bps to 1,200 bps to 2,400 bps to 9,600 bps to 14.4Kbps to 28.8Kbps to, and to 33.6Kbps. Now new modem standards are emerging, reaching speeds of up to 56Kbps. Unlike the 33.6Kbps modems being sold today, 56Kbps is a significant improvement over 28.8Kbps modems. Viewing complex graphics or downloading sound files improves significantly with 56Kbps. The modem experts keep telling us that we are about maxed out. For instance when the 28.8 modems where first introduced they said that we've reached our maximum speed, and the same thing was said about the 33.6 and now again for the 56K, but how true is this? The experts say that the next major improvement will have to come from the telephone companies, when they start laying down fibber-optic cables so we can have integrated services digital network (ISDN) . The thing that makes digital modems better than analog is because with analog modem transmission errors are very frequent which results in your modem freezing or just freaking out. These errors are caused mainly by some kind of noise on the line due to lightning storms, sunspots, and other fascinating electromagnetic phenomena, noise occurs anywhere on the line between your PC and the computer you're communicating with 2,000 miles away. Even if line noise is minimal, most modems will automatically reduce it's speed to avoid introducing data errors. Baud vs bps While taking about modems, the transmission speed is the source of a lot of confusion. The root of the problem is the fact that the terms "baud" and