| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching device which is miniaturized and has a countermeasure against power source shut-down. SOLUTION: A detecting circuit 105 is configured so that it can distinguishably detect a ringing signal and an on-hook signal. When power is not supplied, a telephone set 101 is connected to a telephone line network 108 to receive telephone services. When power is supplied, the telephone set 101 is connected to an IP network 109 and brought into a default state. In this case, upon detecting the ringing signal from the telephone line network 108, the detecting circuit 105 notifies a control unit 106 of the detection. The control unit 106 switches a relay 110 to connect the telephone set 101 to the telephone line network 108. When the telephone set 101 ends a call and is hooked on, the detecting circuit 105 detects the on-hook and notifies the control unit 106 of the detection. The control unit 106 switches the telephone set 101 to the IP network 109 to bring it to the default state. COPYRIGHT: (C)2005,JPO&NCIPI
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