EMERGENCY TELEPHONE CALL MACHINE CHANGING METHOD IN PBX SYSTEM, AND EMERGENCY TELEPHONE CALL MACHINE CHANGING SYSTEM IN PBX SYSTEM

摘要

PROBLEM TO BE SOLVED: To solve the problem that a telephone at each slave station cannot be used as an emergency telephone upon the occurrence of a trouble in a master PBX 1.;SOLUTION: When the master PBX 1 is normal, a master NCU 4 connects an office line 2 of a public network and an input signal line to the master PBX 1 via a relay 431, and a slave NCU 401 connects a telephone 31 of the slave PBX and an output signal line of the slave PBX via a relay 434. Upon a system down of the master PBX 1, a master changing machine 18 transmits change information to the master NCU 4 and the slave NCU 401. When receiving the change information, the master NCU 4 switches between the relays 431 and 432 to connect the office line 2 of the public network and an NCU speech line 8. The slave NCU 401, when receiving the change information, switches between the relays 433 and 434 to connect the NCU talking line 8 and the slave telephone 31.;COPYRIGHT: (C)2004,JPO