| 摘要 |
PURPOSE:To call a called subscriber by keeping a calling subscriber waiting until a busy called subscriber is set in a ring-off state and an extension becomes idle. CONSTITUTION:The subscriber of an extension telephone 3 is set in an off-hook state and wants to have a call to an extension telephone 2. Under such conditions, a central controller 8 controls an originating register/each signal tone transmission circuit 10 as long as the subscriber of the telephone 2 is kept busy. Then the subsequent busy tones are transmitted to set a flag which is kept waiting at a memory element 9. The controller 8 monitors the state transition of a calling subscriber for each prescribed time and decides whether or not a waiting flag is is turned on. If this flag is turned on, it is decided whether or not the subscriber of the telephone 3 hooks off the handset. If the subscriber is kept waiting, the monitor processing is started for the state transition of the called subscriber. |
