| 摘要 |
PURPOSE:To eliminate the need for a call signal source and a special line through which a call signal is sent by using a circuit component in a control circuit of a terminal connection device so as to generate the call signal. CONSTITUTION:When the call state of a terminal equipment 2 is caused by a terminal connection device 1, an X relay is operated at first to disconnect the terminal equipment 2 from a subscriber line 4 and to connect a call signal transmission circuit 3 and the terminal equipment 2. Then a CPU turns on/off a photocoupler A in a period of 31.32ms to energize the call bell of the terminal equipment 2. Simultaneously, the CPU monitors a photocoupler B and when the photocoupler B is set, it is discriminated that the terminal equipment 2 is hooked off to stop the transmission of the call signal and to activate the relay X thereby restoring the terminal equipment 2 to the subscriber line 4.
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