A sender was a circuit in a 20th century electromechanical 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...

 which sent telephone number

Telephone number

A telephone number or phone number is a sequence of digits used to call from one telephone line to another in a public switched telephone network. When telephone numbers were invented, they were short — as few as one, two or three digits — and were given orally to a switchboard operator...

s and other information to another exchange. In some American exchange designs, for example 1XB switch the same term was also used to refer to the circuit that received this information. The corresponding device in the British director telephone system

Director telephone system

The Director System was a system which made it possible to call subscribers at other telephone exchanges without operator intervention in large multi-exchange cities, and to have a mixture of automatic and manual exchanges within these cities...

 was called a "director" and, in other contexts, "register".

See also

• communication source
  Communication source
  A source or sender is one of the basic concepts of communication and information processing. Sources are objects which encode message data and transmit the information, via a channel, to one or more observers ....
  
  
• Director telephone system
  Director telephone system
  The Director System was a system which made it possible to call subscribers at other telephone exchanges without operator intervention in large multi-exchange cities, and to have a mixture of automatic and manual exchanges within these cities...
  
  
• Panel switch
  Panel switch
  The panel switching system was an early type of automatic telephone exchange, first put into urban service by the Bell System in the 1920s and removed during the 1970s...
  
  
• Register signaling
  Register signaling
  In telecommunications, register signaling provides addressing information, such as the calling and/or called telephone number. R2 register signaling is an example.This is contrasted with line signaling....