A telephone interface installed at the customer's premises converting analog signals from the customer's in-home wiring to a digital signal, which is then sent over the cable connection to the company's Cable television headend switching center.
Cable telephone provides another revenue stream for cable television system operators and gives the consumer the convenience of combing several services on a single bill - such as paid television, internet and telephone services.
Other advantages include better voice quality and perhaps future integration to a VoIP network providing cheap or unlimited nationwide and international calling.
One possible disadvantage to digital cable telephone service is similar to a disadvantage of cable Internet access, namely that the medium is shared, which could result in occasional delays and drops when high volumes of bandwidth are used or in some cases shared with entire neighborhoods.
Traditional landline service from phone companies supply phantom power over the communication wires and therefore keep attached devices operational.