A telephone network is a telecommunications network

Telecommunications network

A telecommunications network is a collection of terminals, links and nodes which connect together to enable telecommunication between users of the terminals. Networks may use circuit switching or message switching. Each terminal in the network must have a unique address so messages or connections...

 used for telephone call

Telephone call

A telephone call is a connection over a telephone network between the calling party and the called party.-Information transmission:A telephone call may carry ordinary voice transmission using a telephone, data transmission when the calling party and called party are using modems, or facsimile...

s between two or more parties.

There are a number of different types of telephone network:

• A fixed line network where the telephones must be directly wired into a single telephone exchange
  Telephone exchange
  In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls...
  
  . This is known as the public switched telephone network
  Public switched telephone network
  The public switched telephone network is the network of the world's public circuit-switched telephone networks. It consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all inter-connected by...
  
   or PSTN.
• A wireless network where the telephones are mobile
  Mobile phone
  A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
  
   and can move around anywhere within the coverage area
  Cellular network
  A cellular network is a radio network distributed over land areas called cells, each served by at least one fixed-location transceiver known as a cell site or base station. When joined together these cells provide radio coverage over a wide geographic area...
  
  .
• A private network where a closed group of telephones are connected primarily to each other and use a gateway to reach the outside world. This is usually used inside companies
  Company
  A company is a form of business organization. It is an association or collection of individual real persons and/or other companies, who each provide some form of capital. This group has a common purpose or focus and an aim of gaining profits. This collection, group or association of persons can be...
  
   and call centre
  Call centre
  A call centre or call center is a centralised office used for the purpose of receiving and transmitting a large volume of requests by telephone. A call centre is operated by a company to administer incoming product support or information inquiries from consumers. Outgoing calls for telemarketing,...
  
  s and is called a private branch exchange (PBX).

Public telephone operator

Telephone operator

A telephone operator is either* a person who provides assistance to a telephone caller, usually in the placing of operator assisted telephone calls such as calls from a pay phone, collect calls , calls which are billed to a credit card, station-to-station and person-to-person calls, and certain...

s (PTOs) own and build networks of the first two types and provide services to the public under license from the national government. Virtual Network Operators

Mobile virtual network operator

A mobile virtual network operator is a company that provides mobile phone services but does not have its own licensed frequency allocation of radio spectrum, nor does it necessarily have all of the infrastructure required to provide mobile telephone service...

 (VNOs) lease capacity wholesale from the PTOs and sell on telephony

Telephony

In telecommunications, telephony encompasses the general use of equipment to provide communication over distances, specifically by connecting telephones to each other....

service to the public directly.