Toll Trunking Methods

Call-Circuit Trunking Method.² When a toll call is to be passed, the toll operator at the originating office presses a key that connects her telephone set to a call circuit leading to a toll operator in the desired distant toll office. The distant toll operator assigns a vacant toll channel, or trunk, to the originating operator, and the toll call is completed over this assigned trunk. This procedure has been largely replaced by the method that follows.

Straightforward Trunking Method.² The toll operator at the originating office connects her telephone set to a vacant toll trunk to the desired office. At this office the operator passing the call is connected automatically to an operator who will complete the call. The required information is passed, and the toll connection established, over this same circuit. Note that in the call-circuit method the trunk selection is made by the operator at the terminating office, whereas in the straightforward method the trunk is selected by the originating operator.

Ringdown Trunking Method.² This is used where it is not economical to install the equipment for the straightforward method. In this system the originating operator plugs in on a trunk to the desired city and presses a key which operates a signal at the distant toll switchboard. An operator connects her telephone set to the trunk and answers. The call is then passed to the distant operator and completed by her over the same trunk.

Dial Trunking Method.² In some installations, the operator in the originating office connects to a trunk to the called locality and dials the called number directly.