| 摘要 |
PURPOSE:To prevent the adverse effect due to the superimposition between a control signal and a voice signal by controlling individually a switch changing over two circuits having separate functions to the voice depending on the line side and a handset side. CONSTITUTION:Privacy devices 12, 112 are connected through a telephone line 14 and talked between them in the privacy release state (function A). In operating an operation section 15 at the device 12 to switch the state to the privacy state (function B), after changeover switches 1, 6 are switched to the privacy circuits 2, 7, a switching control signal is sent to an opposite device 112 via a line 14 from the signal transmission section 5. The device 112 receives the signal to switch changeover switches 101, 106 to the position of privacy circuits 102, 107. The devices 12, 112 apply prescribed signal transmission/reception in such a state and when successful, the changeover switches 4, 9, 104, 109 are switched to the position of the privacy circuits 2, 7, 102, 107 to talk in the privacy state.
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