Plain old telephone service, or POTS, are the services available from analogue telephones prior to the introduction of electronic telephone exchanges into the public switched telephone network. These services had been available almost since the introduction of the telephone system in the late 19th 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 duplex, voice path with limited frequency range of 300-3400Hz
• dial tone and ringing signals
• subscriber dialing
• operator services, such as directory assistance and long distance and conference calling assistance

With the advent of electronic telephone exchanges and computerisation during the 1970s and 1980s, a raft of new network services became available. These had been termed PANS for pretty advanced network (or new) services by some in the industry, although that term has never really caught on. The services offered include:

• voice mail
• caller ID
• call waiting
• reminder calls
• (three-way) conference calling
• Enhanced 911

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 thing to note is that while modems up to 56K baud are available to most users, most telephone companies do not guarentee service to that speed on POTS lines as these were not meant to be Data lines. Unfortunately, this is not normally spelled out explicitly leading to unnecessary repair calls.

See also

• RJ-11
• twisted pair
• 25-pair color code

External links

• The Basics of Telephone Wiring (http://telecom.hellodirect.com/docs/Tutorials/TelWiringBasics.1.040401.asp)
• Home Phone Wiring Advice Page (http://www.homephonewiring.com/)
• Doing your own telephone wiring (http://www.ling.upenn.edu/~kurisuto/phone_wiring.html)

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