Plain old telephone service
Plain old telephone service, or POTS, is the standard telephone service that remains the basic form of residential and small business telephone service nearly everywhere in the world, and was the only basic telephone service known to most people until the introduction of mobile phones. It has been available almost since the introduction of the telephone system in the late 19th century, in a form mostly unchanged to the normal user despite the introduction of electronic telephone exchanges into the public switched telephone network since the middle of the 20th century.
The system was originally known as the Post Office Telephone Service or Post Office Telephone System in many countries. The term was dropped as telephone services were removed from the control of national post offices.
POTS services include:
- bi-directional, or full duplex, voice path with limited frequency range of 300 to 3400 Hz: in other words, a signal to carry the sound of the human voice both ways at once;
- call-progress tones, such as dial tone and ringing signal;
- subscriber dialing;
- operator services, such as directory assistance and long distance and conference calling assistance;
- a standards compliant analog telephone interface including BORSCHT functions;
With the advent of electronic telephone exchanges and computerization during the 1970s and 1980s, a raft of new network services became available. These were termed PANS for pretty advanced network (or new) services by some in the telephony industry, although that term has not been used widely. The services offered include:
- voice mail
- caller ID
- call waiting
- reminder calls
- (three-way) conference calling
- Enhanced 911
- Centrex
and a number of other similar services.
The new services were made possible by the introduction of the support network for the ISDN as well as raised consumer expectations from services offered on mobile telephones.
One notable fact is that while modems capable of operating at up to 56 kilobits per second are available, most telephone companies do not guarantee service to that speed on POTS lines since these lines were not meant to be data lines. Unfortunately, this is not normally spelled out explicitly, leading to some unnecessary repair calls.
Reliability
While POTS provides a relatively limited feature set, low bandwidth and no mobile capabilities, it does provide (in most geographic areas) much greater reliability than any of the more “modern” telephone systems (wireless, cellular, VoIP, etc). This can be illustrated with the following demonstration: pick up a standard “old-fashioned” telephone and dial a valid number - you will, nearly 100% of the time, be connected to the desired party (provided they are available). This is more than can be said for almost any other communication system. [citation needed]
See also
- Public switched telephone network
- RJ11 - the type of telephone jack common in North America for single line POTS telephones
- DTMF - the tones used for button dialing
- 25-pair color code
- ADSL
- Filter
- Twisted pair
- Foreign exchange office (FXO)
- Foreign exchange station (FXS)