Modems area unit typically classified by the quantity of information they'll send a given unit of your time, sometimes expressed in bits per second (symbol bit/s, generally abbreviated "bps"), or bytes per second (symbol B/s). Modems also can be classified by their image rate, measured in baud rate. The baud rate unit denotes symbols per second, or the quantity of times per second the electronic equipment sends a brand new signal. as an example, the ITU V.21 commonplace used frequence shift keying with 2 attainable frequencies, akin to 2 distinct symbols (or one bit per symbol), to hold three hundred bits per second mistreatment three hundred baud rate. By contrast, the original ITU V.22 standard, which could transmit and receive four distinct symbols (two bits per symbol), transmitted 1,200 bits by sending 600 symbols per second (600 baud) using phase shift keying.
A electronic equipment (modulator-demodulator) could be a device that modulates signals to write digital info and demodulates signals to decrypt the transmitted info. The goal is to supply a sign which will be transmitted simply and decoded to breed the first digital information. Modems may be used with any means that of transmittal analog signals, from light-weight emitting diodes to radio. a standard kind of electronic equipment is one that turns the digital information of a laptop into modulated electrical signal for transmission over phonephone lines and demodulated by another electronic equipment at the receiver facet to recover the digital information.