| 摘要 |
PROBLEM TO BE SOLVED: To inform even a remote user of a telephone set of a time to replace a battery by superimposing an alarming sound on a speech signal so as to allow the user to recognize that the remaining battery power is small. SOLUTION: When a terminal adapter TA1 receives power supply from a back up battery 12 at the time of power interruption, a remaining battery power monitoring part 13 informs a control part 14 that the remaining power is less than a prescribed value. The part 14 instructs a warning display part 15 to flicker and instructs also an alarm generating part 16 to issue an alarming sound of an audible frequency to be superimposed by a speech signal superimposing 18 on a speech signal from ISDN received by a network control part 17 to be sent to to telephone sets 3A and 3B from an analog port control part 19. Thus, it is possible to allow even a user of a telephone set at a place remote from TA1 to recognize that the remaining power of the battery is small. |
