普通市内电话有的双机并接,共用一条线路,一个号码。当甲机工作时,乙机会听到甲机的谈话内容,严重影响了电话保密。为了解决这一问题,现介绍一个简单电路,可以实现电话主、副机自动转换,不受另一部话机的干扰,以保证通话的保密性。本电路采用优先式,不影响同时振铃。当甲机先拿起话筒时,J_1继电器工作翻转,触点J_1由开转为合,J_1由合转为开,完全切断乙机。只要甲机挂上电话,乙机就能立即恢复工作。如乙机拿起话筒,J_2继电器工 Some ordinary city phone and double-parallel, share a line, a number. When a machine is working, B will hear the contents of a machine conversation, seriously affecting the telephone confidentiality. In order to solve this problem, we now introduce a simple circuit that can achieve the main phone, vice automatic conversion from another phone to ensure the confidentiality of the call. This circuit takes precedence, does not affect the simultaneous ringing. When a machine picked up the first microphone, J_1 relay work flip, contact J_1 from open to close, J_1 by the combined turn on, completely cut off the B machine. As long as a machine hang up, B machine can resume work immediately. If B pick up the microphone, J_2 relay workers