| 摘要 |
PURPOSE:To simplify the handling of a plug-in system telephone set by providing a method of discriminating between the on-hook state and disconnection state of the telephone set. CONSTITUTION:When the mobile telephone set is not plugged into the socket, a current of a specific frequency sent out from the oscillator of telephone-set connection detector C flows to only calling detection circuit B, where constant current I1 is detected. Once the telephone set is connected, the current of the specific frequency flows to telephone-set circuit A as well, so that the value of the current flowing to the detector will vary. By detecting this, the detector finds the connection of the telephone set. Afterwards, a subscriber informs a switchboard of its own telephone number to register the telephone number. |
