| 摘要 |
PURPOSE:To register an extension subscriber number which is given to each extension subscriber fixedly before in an optional telephone set by registering subscriber information on an extension telephone set through which each extension subscriber should receive an incoming call corresponding to extension subscribers. CONSTITUTION:A main memory device (MM) 8 has a memory 80 for storing subscriber numbers ST given to respective extension subscribers and a memory 81 for storing subscriber information registered by extension subscribers SN01-SNn, i.e., extension telephone set group number GR. When the extension subscriber SN01 registers GR#1, the GR#1 is registered in the SN01 corresponding area in the memory 81. When there is an incoming call from a calling subscriber to an extension subscriber A, a central controller CC 7 discriminates the N01, reads the GR#1 out of the memory 81, and controls a switch SW 4 to connect the calling subscriber to an extension telephone set 1 belonging to the GR#1. If there is incoming to the extension subscriber A while the extension subscriber A does not register the GR#i, the CC 7 controls the SW 4 to connect the calling subscriber to an announcing device ANM 6, thereby sending a message indicating that the extension subscriber A is absent to the calling subscriber.
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