Device that connects to a cable television line to provide a continuously available broadband data connection.

Modem is short for modulator/demodulator and refers to the method of transmitting digital data over an analogue circuit.

Data signals in a digital cable system are transmitted over radio frequency or RF carrier signals. For two-way communication, one carrier signal carries data downstream from the cable network to the customer and another carries data upstream from the customer to the cable network.

Cable modems are devices at the subscriber premises that convert digital information into a modulated RF signal in the upstream direction and convert the RF signals to digital information in the downstream direction.

A Cable Modem Termination System or CMTS performs the converse operation for multiple subscribers at the cable operator.

DOCSIS provides a standard specification for cable modems.