(C) A modem is a hardware device that converts data between transmission media so that it can be transmitted from computer to computer(historically over telephone wires). Modems can be used with any means of transmitting analog signals, from light emitting diodes to radio. A common type of modem is one that turns the digital data of a computer into a modulated electrical signal for transmission over telephone lines and demodulated by another modem at the receiver’s side to recover the digital data.