| 摘要 |
PURPOSE:To avoid a troublesome phone call by activating a telephone set only to a talking in which a secret signal is transmitted. CONSTITUTION:When a transmission side telephone set 8 is dialed, a current operating a call bell is sent from a telephone exchange 13 to a reception side telephone set. In throwing a changeover switch 5 to the position (a), the telephone set is activated normally. In throwing the switch 5 to a terminal (b), a secret signal transmission guide circuit 9 guides the titled device so as to transmit a secret signal toward a telephone set 10. The transmission side guided by the transmission of the signal S in this way sends the signal S. When the signal S is sent, it is received by a secret signal reception drive circuit 12. Since the signal S is the same as a predetermined signal, the circuit 12 drives a switch 11 and flows a current I to the telephone set 8 to ring a call bell of the telephone set 8. Since the call bell of the telephone set 8 is rung in this way, the talking with a telephone is attained.
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