Modem stands for modular – demodulator. It is a mechanism that adjusts an analog carrier signal to program digital information as well as to extract the carrier signal to decipher the information that was transmitted. The aim is to generate a signal that can easily transmit, decode and replicate the original digital data. Modems can be used over any means of transmitting analog signals from driven diodes to radio. The most recognizable instance is a voice band modem that turns the digital 1s and 0s of a personal computer into sounds that can be transmitted over the telephone lines of plain old telephone services (POTS). Once the sound is received on the other side the 1s and 0s will be transformed into a form that is used by a Serial, USB, Ethernet or network connection.
The amount of data that can be sent in a given time is what generally classifies modems. The data is usually measured in bits per second (bps). The number of times the modem alters its signal state per second is a classification as well.
Internet users use modems that are faster specifically ADSL modems and cable modems. Wide – band radio modems transmit repeating frames of data at extremely high data rates over microwave radio links, in telecommunications. Narrow band radio modem is used for low data rate up to 19.2.k chiefly for private radio networks. A few modems used by microwaves transmit over a hundred million bits per second. The concept Data – Phone was incepted sometime in the 1960s and it replaced the previous term digital subset.
Bell Labs introduced the Bell 103A dataset standard in 1962 and it supplied full – duplex service at 300 baud over normal phone lines.
Before 1968 AT&T was a monopoly in the United States as it related to use of its telephone lines. Only Bell – supplied devices could be connected to AT&T’s network. This ultimately led to the emergence of 103A compatible modems. These were mechanically connected to the through the handset, this was called acoustically coupled modems.