| 摘要 |
A break-in method and a circuit in a key system for switching a key system to a conference-call state by use of a conference-call circuit is disclosed in the invention. In the break-in method, when an attendant perceives a telephone subscriber on the line, the attendant breaks in forcefully upon the subscriber's call currently on the line, changing the present call to a conference call. Thereafter, if the attendant hangs on the phone, the subscriber having waited for being switched breaks into the conference-call replacing the attendant. To achieve the improved method the inventive subject includes: a microprocessor MPU for controlling the key system; a subscriber circuit SBC for interfacing a state of an extension-line subscriber ST1 to STn with a main system 100; an office line circuit OLC for interfacing office-line codes Co1, Co2 with the main system 100; a switching circuit S/W for providing and switching a line controlling under control microprocessor MPU; a conference-call circuit CFC for providing telephone subscribers with the conference-call operation by means of controlling microprocessor MPU; and a memory MRY for reading and writing data by controlling under control microprocessor MPU.
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