| 摘要 |
PROBLEM TO BE SOLVED: To store a telephone number of the other party of speech when functions of a main device gets unavailable, and to switch from an alternative outside line to a normal line for use without terminating a call after restoration from a fault. SOLUTION: An extension telephone with an alternative outside line connection function, which is connected to an extension of the main device accommodating outside lines and extensions, is connected to an extension interface of the main device in a normal state, and is switched to an outside interface for alternative (line for use at faults) to originate and terminate calls when a fault of the main device, a power failure, or the like occurs. In the case that a fault occurs in the main device during speech and the extension telephone is switched to the outside line interface, the extension telephone automatically originates a call to the other party of the speech through an alternative outside line or automatically transmits a voice message informing of the occurrence of abnormality when automatically originating the call. COPYRIGHT: (C)2009,JPO&INPIT
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