In older telephone systems, this was a long-distance call that required routing across high-capacity intercity lines, known as trunks. Callers typically had to dial an operator to request the connection, which incurred toll charges based on distance and duration. The terminology persists in some regions and in the underlying engineering of switching networks, where trunk lines still carry aggregated traffic between exchanges.
We had to book a trunk call through the operator just to talk to the head office in London.
While the phrase is mostly historic for consumers, telecom engineers still use the word trunk to describe the thick fiber or copper links connecting major network nodes.
Also heard as
- toll call
- long-distance call
Related terms
Exchange
A physical building or the specific set of telephone numbers routed through it.
Telephone exchange
A central system of switches that routes calls between subscribers.
PSTN
The global infrastructure of circuit-switched telephone networks operated by national and regional carriers.
Subscriber trunk dialling
The automated telephone exchange system that allows callers to dial long-distance numbers directly.