Cable telephony is a form of

digital telephony Telephony ( ) is the field of technology involving the development, application, and deployment of telecommunications services for the purpose of electronic transmission of voice, fax, or data, between distant parties. The history of telephony is ...

over

cable TV Cable television is a system of delivering television broadcast programming, programming to consumers via radio frequency (RF) signals transmitted through coaxial cables, or in more recent systems, light pulses through fibre-optic cables. This ...

type networks. 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. The signal is then sent on to the

public switched telephone network The public switched telephone network (PSTN) is the aggregate of the world's telephone networks that are operated by national, regional, or local telephony operators. It provides infrastructure and services for public telephony. The PSTN consists o ...

(PSTN). 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. Richard Grigonis (ed) ''Cable Telephony'' in ''Computer Telephony Encyclopedia'', Focal Press, 2000 pp.68-69 At times in the industry this is referred to as "

triple play In baseball or softball, a triple play (denoted as TP in baseball statistics) is the act of making three out (baseball), outs during the same play. There have only been 739 triple plays in Major League Baseball (MLB) since 1876, an average of ju ...

Emergency calls

The biggest obstacle to cable telephone service is the need for nearly 100% reliable service for

emergency call An emergency telephone number is a number that allows a caller to contact local emergency services for assistance. The emergency number differs from country to country; it is typically a three-digit number so that it can be easily remembered and ...

s. 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 Quality of service (QoS) is the description or measurement of the overall performance of a service, such as a telephony or computer network, or a cloud computing service, particularly the performance seen by the users of the network. To quantitat ...

demands of traditional analog telephone service.

Advantage

The biggest advantage to digital cable telephone service is similar to the advantage of

digital cable Digital cable is the distribution of cable television using digital data and video compression. The technology was first developed by General Instrument. By 2000, most cable companies offered digital features, eventually replacing their previo ...

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 Voice over Internet Protocol (VoIP), also known as IP telephony, is a set of technologies used primarily for voice communication sessions over Internet Protocol (IP) networks, such as the Internet. VoIP enables voice calls to be transmitted as ...

network providing cheap or unlimited nationwide and international calling. In most cases, digital cable telephone service is separate from

broadband Internet access In telecommunications, broadband or high speed is the wide- bandwidth data transmission that exploits signals at a wide spread of frequencies or several different simultaneous frequencies, and is used in fast Internet access. The transmission m ...

service being offered by many cable companies and does not rely on IP traffic or the

Internet The Internet (or internet) is the Global network, global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a internetworking, network of networks ...

Disadvantage

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. These delays could be experienced during the "prime time" parts of the day, when heavy Internet usage and Internet streaming devices can make telephone calls on this system difficult. However, by utilizing Cable Lab's Packet Cable interface specifications, cable operators are able to diminish the effects of heavy internet usage on call quality. This is done by way of QoS provisions present in the Packet Cable specifications.
PacketCable™ Dynamic Quality-of-Service Specification. The second disadvantage it that this service requires power at the subscriber's end. In an emergency, if mains power is lost and without the battery backup unit provided at an additional cost by the cable provider, this telephone service ceases to function. Traditional landline service from phone companies supply

phantom power Phantom power, in the context of Professional audio, professional audio equipment, is Direct current, DC electric power equally applied to both signal wires in Balanced line, balanced microphone cables, forming a phantom circuit, to power m ...

over the communication wires and therefore keep attached devices operational.

References

{{Authority control Telephony Cable television technology