| 摘要 |
PURPOSE:To immediately use either of a handset and a headset for speaking by detecting connection of a transmitter-receiver to a connector for transmitterreceiver connection, which is connected to a telephone line in the on-hook state, to connect this connector to the telephone line. CONSTITUTION:When a manual switch 11 in a switch box 10 is turned on without hooking off a handset 28, a headset 29 is connected to a second modular connector 8, and a current flows to the headset 29 from a line 7 through the second modular connector 8 and the manual switch 11. When detecting the current flowing to the line, a current detecting circuit 6 applies a signal indicating turningon to a switch circuit 5. When this signal is inputted, the circuit 5 is turned on to short-circuit both ends of a first hook switch 2. Consequently, the off-hook state is set though first and second hook switches 2 and 4 are turned off, and calling and response to incoming call are possible.
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