My Creation

Modems

Standard telephone linens can transmit only analog signals, computers, however stores and transmit data digitally. Modem can transmit digital computer signals over telephone lines by converting them to analog form.

Converting one signal from to another (digital to analog in this case) is called modulation. Recovering the original signal is called demodulation. The word “Modem” derives from the terms modulation/demodulation.

Modem can be used to connect computer devices or entire networks that are at distant locations (Before digital telephone lines existed modem were about the only way to link distant devices).

Some modems operate constantly over dedicated phone lines. Others use standard public switched-telephone network (PSTA) dial-up lines and make a connection only where one is required.

Modem enable networks to exchange email and to perform limited data transfers, but the connecting made possible is extremely limited due to limited bandwidth to connect to remote network, like a routers to directly exchange data. Instead modem act like network cards in that they provide an access point onto the transmission medium, in this case the telephone lines, in order to send analog signals to another device, most likely another modem, on the network.

Until recently, modem manufacturers used a parameter called baud rate to gauge modem performance. The baud rate is the oscillation speed of the sound wave transmitted or received by the modem. Although baud rate is still an important parameter, recent advances in compression technology have made it less meaningful. Some modems now provide a data transfer rate (in bits per second-a more measure of network performance) that exceeds the baud rate. In other words, you can no longer assume the baud rate and the data transfer rate are equal.

Modems are classified according to the transmission method they use for sending and receiving data. The two basic types of modems are as follows: