The modem is a piece of equipment utilised for transferring data between two computers over telephone lines. Because standard telephone networks may be used, computer information can be sent around the globe almost instantaneously. The name modem is actually a shortened version of the name modulator/demodulator. In order to send information the digital computer data must be modulated. This basically means it must be altered from its digital state to an analogue state which may then be transmitted down the telephone line. The information, when received, is demodulated, or returned to its digital state to be stored in the receiving computer's memory, ready for use.
The first modems were very slow in transmitting data and were connected to telephone systems via rubber cups which fitted over the telephone handset's mouthpiece and earpiece. They were termed acoustically coupled modems and tended to be very unreliable. Modern modems achieve much higher speeds of transmission and plug directly into the telephone system. These modems feature automatic error correction and data compression making them fast and reliable.
