First modem

Released by AT&T Corporation (USA) in 1958, the Bell 101 was the first modem (modulator-demodulator) for transferring digital data between computers via analogue networks such as telephone cables. It was initially used by the SAGE (Semi-Automatic Ground Environment) air-defence system, which comprised several military radar stations that sought to coordinate their data to produce an uninterrupted view of the skies over North America. It was made commercially available in 1959. The Bell 101 modem allowed digital data to be transmitted over regular unconditioned telephone lines at a speed of 110 bits per second. By 1962, it had been superseded by the next model, the Bell 103, the modulation for which is still in use to this day.