Cable telephony is a specialized form of digital telephony over cable TV networks accomplished by installing a special telephone interface at the customer's premises that converts the analog signals from the customer's in-home wiring into a digital signal, which is then sent over the cable connection to the company's switching center, where it is connected to the PSTN.

The biggest obstacle to cable telephone service is the need for nearly 100% reliable service for emergency calls. PacketCable, one of the emerging standards being developed for digital cable telephony, seems to be the most promising and able to work with the Quality of Service demands of traditional analog telephone service.

The biggest advantage to digital cable telephone service is similar to the advantage of digital cable television, namely that data can be compressed, resulting in much less bandwidth used than a dedicated analog circuit-switched service. Other advantages include better voice quality and perhaps future integration to a VoIP network providing cheap or unlimited nationwide and international calling. Note that in most cases, digital cable telephone service is separate from broadband internet service being offered by many cable companies and does not rely on TCP/IP traffic or the Internet.

de:Voice over Cable