Telephone number in the context of "Telephone exchange"

Greece has a national telephone numbering plan with ten-digit telephone numbers. The first digit represents the type of service. 1 is used for short codes, 2 for geographical numbers (3 and 4 are reserved for that purpose too), 5 is used for inter-network routing purposes (non-dialable codes) and VPNs, 6 for mobile services, 7 is reserved for universal access numbers (not active), 8 for reduced-fee services (like 800 toll-free, 801 local call, 89 dial-up and data services), 9 is used for premium rate services (901 for general purpose and 909 for adult-only services). All dialable numbers are ten digits, except for short codes (3–5 digits in the 1 range), 807-XXXX (seven digits) used for calling card access codes, and numbers in the 5 range, used for routing purposes and not dialable by end-subscribers.

A telephone numbering plan is a type of numbering scheme used in a telecommunications network to assign telephone numbers to subscriber telephones or other telephony endpoints. Telephone numbers are the addresses of participants in a telephone network, reachable by a system of destination code routing. Telephone numbering plans are defined world-wide, as well as within each of the administrative regions of the public switched telephone network (PSTN), and in private telephone networks.

In public numbering systems, geographic location typically plays a role in the sequence of numbers assigned to each telephone subscriber. Many numbering plan administrators subdivide their territory of service into geographic regions designated by a prefix, often called an area code or city code, which is a set of digits forming the most-significant part of the dialing sequence to reach a telephone subscriber. Within such regions designated by area codes, locally unique telephone numbers are assigned based on locally determined principles but in agreement with the larger-network rules.

Premium-rate telephone numbers are telephone numbers that charge callers higher price rates for select services, including information and entertainment. A portion of the call fees is paid to the service provider, allowing premium calls to be an additional source of revenue for businesses. Tech support, psychic hotlines, and adult chat lines (e.g. dating and phone sex) are among the most popular kinds of premium-rate phone services. Other services include directory enquiries, weather forecasts, competitions and ratings televoting (especially relating to television shows). Some businesses, e.g. low-cost airlines, and diplomatic missions, such as the US Embassy in London or the UK Embassy in Washington, have also used premium-rate phone numbers for calls from the general public.

Premium calls are typically independent of the caller's area code. These telephone numbers are usually allocated based on a national telephone numbering plan that makes them easily distinguishable from non-premium numbers; telephone companies often offer their customers the option to block calls from these number ranges, and in some jurisdictions, are required by law to offer blocking services.

A sender is a type of circuit and system module in 20th-century electromechanical telephone exchanges. It registered the telephone numbers dialed by the subscriber, and transmitted that information to another part of the exchange or another exchange for the purpose of completing a telephone call. Some American exchange designs, for example, of the No. 1 Crossbar switch used originating senders and terminating senders. The corresponding device in the British director telephone system was called a "director" and, in other contexts, "register".

Dial-up Internet access is a form of Internet access that uses the facilities of the public switched telephone network (PSTN) to establish a connection to an Internet service provider (ISP) by dialing a telephone number on a conventional telephone line which could be connected using an RJ-11 connector. Dial-up connections use modems to decode audio signals into data to send to a router or computer, and to encode signals from the latter two devices to send to another modem at the ISP.

Dial-up Internet reached its peak popularity during the dot-com bubble. This was in large part because broadband Internet did not become widely used until well into the 2000s. Since then, most dial-up access has been replaced by broadband.

In telecommunications, directory enquiries or directory assistance is a phone service used to find out a specific telephone number and/or address of a residence, business or government entity.

The Suicide and Crisis Lifeline in the United States, or Suicide Crisis Helpline in Canada, and formerly known as the National Suicide Prevention Lifeline, is a suicide prevention and crisis help line to a network of a large number of crisis centers in the United States and Canada that provide 24/7 service via a toll-free hotline and with the three-digit short code telephone number 9-8-8.

In the United States, the 988 short code was implemented in July 2022 as an addition to its predecessor, a 1-800 number that existed since 2005. Calls to the hotline are routed to the nearest crisis center that provides immediate counseling and a referral to a local mental health service. The service supports people who call for their own crisis or for someone they care about.

E.164 is an international standard (ITU-T Recommendation), titled The international public telecommunication numbering plan, that defines a numbering plan for the worldwide public switched telephone network (PSTN) and some other data networks.

E.164 defines a general format for international telephone numbers. Plan-conforming telephone numbers are limited to only digits and to a maximum of fifteen digits. The specification divides the digit string into a country code of one to three digits, and the subscriber telephone number of a maximum of twelve digits.