| 摘要 |
PROBLEM TO BE SOLVED: To hold a call in a speaking state when it exists at the time of power restoration and to speedily perform the restoration changeover of a system when power is restored. SOLUTION: When the call in the middle of speaking exists if a telephone exchange 12 is restored from a complete power cut state, a call detection part 9 in an ISDN power cut switch device 1 detects that telephone sets 15 and 16 are in the middle of speaking, maintains line changeover switches 2, 10 and 11 to a power stop side until they become a termination state and holds the speaking state. A control CPU 4 blocks a call times detection part 21 when the call of the telephone sets 15 and 16 is terminated. Then, next calling/ incoming call are restricted and the ISDN switch device 1 can be switched to a regular state from a power cut state at appropriate timing after the telephone exchange 12 is normally restored.
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