Q. Illustrate Diffrent types of modems?

There are four different types of modems: half-duplex, full-duplex, synchronous, and asynchronous.With half-duplex modems data can be transmitted in only one direction at a time. Full- duplex modems transmit data in both directions at the same time; one modem is designated as the originating modem and the other as the answering modem, while transmitting and receiving data are done at different frequencies. Asynchronous modems are low-data-rate modems transmitting serial data at a rate of about 1800 bits per second (bps). Synchronous modems are high-data-rate modems transmitting serial data at a rate of about 10,800 bps.

Modems can also be classified as voice-band or wide-band modems. Voice-bandmodems are low-to-high speedmodems designed for use on dial-up, voice-grade, standard telephone lines up to a rate of about 10,800 bps.Microprocessor-controlledmodems are known as smart modems, such as the Hayes modem, manufactured by Hayes Microcomputer Products. The portable acoustic- coupler device, which is a different type of voice-band modem, is a low-speed modem with a rate of about 600 bps that is connected acoustically to a standard telephone. Wide-band modems are very high-speed modems with rates of 19,200 bps and above, designed for use with dedicated telephone lines. These are currently used mostly on private communications systems.