modem digital information, and alsotransmitted information.

1. A modem (modulator-demodulator) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information.
2. Modems are generally classified by the amount of data they can send in a given time unit, normally measured in bits per second (bit/s, or bps)
3. They can also be classified by the symbol rate measured in baud, the number of times the modem changes its signal state per second.
4. Modems grew out of the need to connect teletype machines over ordinary phone lines instead of more expensive leased lines which had previously been used for current loop-based teleprinters and automated telegraphs.
5. The next major advance in modems was the Smart modem, introduced in 1981 by Hayes Communications. The Smart modem was an otherwise standard 103A 300-bit/s modem,
6. A Win modem or soft modem is a stripped-down modem that replaces tasks traditionally handled in hardware with software.
7. A standard modem of today contains two functional parts: an analog section for generating the signals and operating the phone, and a digital section for setup and control.
8. The standard digital transmission in modern networks is 64 knit/s but some networks use a part of the bandwidth for remote office signaling
9. Wireless modems come in a variety of types, bandwidths, and speeds. Wireless modems are often referred to as transparent or smart.
10. Smart modems come with a media access controller inside which prevents random data from colliding and resend data that is not correctly received.
11. Voice modems are regular modems that are capable of recording or playing audio over the telephone line. They are used for telephony applications. See Voice modem command set for more details on voice modems.