Plain old telephone service

Plain old telephone service (POTS) is the voice-grade telephone service that remains the basic form of residential and small business service connection to the telephone network in many parts of the world.

The name is a retronym, and is a reflection of the telephone service still available after the advent of more advanced forms of telephony such as ISDN, mobile phones and VoIP. POTS has been available almost since the introduction of the public telephone system in the late 19th century, in a form mostly unchanged to the normal user despite the introduction of Touch-Tone dialing, electronic telephone exchanges and fiber-optic communication into the public switched telephone network (PSTN).

POTS includes:

bi-directional, or full duplex, voiceband 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, long distance calling, and conference calling assistance;
a standards-compliant analog telephone interface including BORSCHT functions

In the United States and Australia, the pair of wires (RJ25 Connector in Australia) from the central switch office to a subscriber's home is called a subscriber loop. It is typically powered by −48V direct current (DC) and backed up by a large bank of batteries (connected in series) and in some cases, an additional electric generator in the local exchange, resulting in continuation of service during most commercial power outages. The subscriber loop typically carries a "load" of about 300 ohms, and does not pose a threat of electrocution to human beings (although shorting the loop can be felt as an unpleasant sensation).

Many calling features became available to POTS subscribers after computerization of telephone exchanges during the 1970s and 1980s. The services include:

Voicemail
Caller ID
Call waiting
Speed dialing
Conference call (three-way calling)
Enhanced 911
Centrex
and other services.

The communications circuits of the PSTN continue to be modernized by advances in digital communications; however, other than improving sound quality, these changes have been mainly transparent to the POTS customer. In most cases, the function of the POTS local loop presented to the customer for connection to telephone equipment is practically unchanged and remains compatible with old Pulse dialing telephones, even ones dating back to the early 20th century.

Due to the wide availability of POTS, new forms of communications devices such as modems and facsimile machines are designed to use POTS to transmit digital information.

Reliability [edit]

While POTS provides limited features, low bandwidth and no mobile capabilities, it provides greater reliability than other telephony systems (mobile phone, VoIP, etc.). Many telephone service providers attempt to achieve "dial-tone availability" more than 99.999% of the time the telephone is taken off-hook. This is an often cited benchmark in marketing and systems-engineering comparisons, called the "five nines" reliability standard. It is equivalent to having a dial-tone available for all but about five minutes each year.

Carriers [edit]

ILEC [edit]

CLEC [edit]

See also [edit]

Public switched telephone network
Managed Facility Voice Network
RJ11 - the type of telephone jack common in most of the world for single line POTS telephones
DTMF - the tones used for pushbutton dialing
Local telephone service
Category 1 cable
Twisted pair
25-pair color code
Foreign exchange office (FXO)
Foreign exchange station (FXS)
Network interface device

Network topology

Switching

v t e Telecommunications in Africa

Sovereign states	Algeria Angola Benin Botswana Burkina Faso Burundi Cameroon Cape Verde Central African Republic Chad Comoros Democratic Republic of the Congo Republic of the Congo Djibouti Egypt Equatorial Guinea Eritrea Ethiopia Gabon The Gambia Ghana Guinea Guinea-Bissau Ivory Coast (Côte d'Ivoire) Kenya Lesotho Liberia Libya Madagascar Malawi Mali Mauritania Mauritius Morocco Mozambique Namibia Niger Nigeria Rwanda São Tomé and Príncipe Senegal Seychelles Sierra Leone Somalia South Africa South Sudan Sudan Swaziland Tanzania Togo Tunisia Uganda Zambia Zimbabwe

States with limited recognition	Sahrawi Arab Democratic Republic Somaliland

Dependencies and other territories	Canary Islands / Ceuta / Melilla / Plazas de soberanía (Spain) Madeira (Portugal) Mayotte / Réunion (France) Saint Helena / Ascension Island / Tristan da Cunha (United Kingdom) Western Sahara

v t e Telecommunications in Asia

Sovereign states	Afghanistan Armenia Azerbaijan Bahrain Bangladesh Bhutan Brunei Burma (Myanmar) Cambodia People's Republic of China Cyprus East Timor (Timor-Leste) Egypt Georgia India Indonesia Iran Iraq Israel Japan Jordan Kazakhstan North Korea South Korea Kuwait Kyrgyzstan Laos Lebanon Malaysia Maldives Mongolia Nepal Oman Pakistan Philippines Qatar Russia Saudi Arabia Singapore Sri Lanka Syria Tajikistan Thailand Turkey Turkmenistan United Arab Emirates Uzbekistan Vietnam Yemen

States with limited recognition	Abkhazia Nagorno-Karabakh Northern Cyprus Palestine South Ossetia Taiwan

Dependencies and other territories	British Indian Ocean Territory Christmas Island Cocos (Keeling) Islands Hong Kong Macau

v t e Telecommunications in Europe

Sovereign states	Albania Andorra Armenia Austria Azerbaijan Belarus Belgium Bosnia and Herzegovina Bulgaria Croatia Cyprus Czech Republic Denmark Estonia Finland France Georgia Germany Greece Hungary Iceland Ireland Italy Kazakhstan Latvia Liechtenstein Lithuania Luxembourg Macedonia Malta Moldova Monaco Montenegro Netherlands Norway Poland Portugal Romania Russia San Marino Serbia Slovakia Slovenia Spain Sweden Switzerland Turkey Ukraine United Kingdom

States with limited recognition	Abkhazia Kosovo Nagorno-Karabakh Northern Cyprus South Ossetia Transnistria

Dependencies and other territories	Åland Faroe Islands Gibraltar Guernsey Jersey Isle of Man Svalbard

Other entities	European Union

v t e Telecommunications in North America

Sovereign states	Antigua and Barbuda Bahamas Barbados Belize Canada Costa Rica Cuba Dominica Dominican Republic El Salvador Grenada Guatemala Haiti Honduras Jamaica Mexico Nicaragua Panama Saint Kitts and Nevis Saint Lucia Saint Vincent and the Grenadines Trinidad and Tobago United States

Dependencies and other territories	Anguilla Aruba Bermuda Bonaire British Virgin Islands Cayman Islands Curaçao Greenland Guadeloupe Martinique Montserrat Navassa Island Puerto Rico Saint Barthélemy Saint Martin Saint Pierre and Miquelon Saba Sint Eustatius Sint Maarten Turks and Caicos Islands United States Virgin Islands

v t e Telecommunications in Oceania

Sovereign states	Australia East Timor (Timor-Leste) Fiji Indonesia Kiribati Marshall Islands Federated States of Micronesia Nauru New Zealand Palau Papua New Guinea Samoa Solomon Islands Tonga Tuvalu Vanuatu

Dependencies and other territories	American Samoa Christmas Island Cocos (Keeling) Islands Cook Islands Easter Island French Polynesia Guam Hawaii New Caledonia Niue Norfolk Island Northern Mariana Islands Pitcairn Islands Tokelau Wallis and Futuna

v t e Telecommunications in South America

Sovereign states	Argentina Bolivia Brazil Chile Colombia Ecuador Guyana Paraguay Peru Suriname Trinidad and Tobago Uruguay Venezuela

Dependencies and other territories	Aruba Bonaire Curaçao Falkland Islands French Guiana South Georgia and the South Sandwich Islands

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Information source: wikipedia.org

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