In telecommunication

Telecommunication

Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...

, a toll switching trunk or toll connecting trunk is a trunk connecting one or more end offices to a toll center as the first stage of concentration for intertoll or long distance traffic.

Operator assistance

Operator assistance

An operator-assisted call is one in which the calling party places a telephone call which requires an operator to provide some form of assistance in completing the call...

 or participation may be an optional function. In U.S. common carrier

Common carrier

A common carrier in common-law countries is a person or company that transports goods or people for any person or company and that is responsible for any possible loss of the goods during transport...

 telephony

Telephony

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

 service, a toll center designated Class 4C is an office where assistance in completing incoming calls is provided in addition to other traffic; a toll center designated Class 4P is an office where operators handle only outbound calls, or where switching

Switching

LAN switching is a form of packet switching used in local area networks. Switching technologies are crucial to network design, as they allow traffic to be sent only where it is needed in most cases, using fast, hardware-based methods.- Layer 2 switching :...

 is performed without operator assistance

Operator assistance

An operator-assisted call is one in which the calling party places a telephone call which requires an operator to provide some form of assistance in completing the call...

.