Method of making a call reservation and sending an interrupt tone in a private branch exchange (PBX)

摘要

Disclosed is a method that gives a priority service to enable a subscriber with an urgent message to call another subscriber who is already engaged in a telephone conversation, regardless of the reservation order, and sends an interrupt tone regularly to the target subscriber as a notification that he has a priority reservation and the subscriber engaged in the telephone conversation can link himself with the priority subscriber without having to cut off the current telephone conversation. The method comprises a plurality of control sequences performed in accordance with the attached flow chart figures.