Indialing to PBX extensions: Application in a step-by-step central office area

Up to the present time, the completion of an incoming call to a private branch exchange (PBX) extension telephone has been dependent upon a human attendant. She must determine what extension station is desired and do the proper switching of the call from the incoming trunk to the station. Indialing provides a means whereby the call is dialed directly from the general exchange system to the PBX station without the need for a human attendant, except for transfer and information services.