| 摘要 |
PURPOSE:To prevent leaking of conversation and noise because of forgetting operation by starting always from the state fixed to receiving state when starting operation after receiving call. CONSTITUTION:A call signal from a speaking equipment of a person on the other terminal of the line comes in from a receiving terminal and inputted to an operation state storing circuit 6. An on signal is outputted from the operation state storing circuit 6 to a voice switch circuit 5, and at the same time, a signal that sets a privacy switch state storing circuit 8 to privacy telephone state is outputted. On the other hand, output from the privacy switch state storing circuit is inputted to an AND circuit 9 and controlled not to transmit a signal that turns sending side switch 2 outputted from the voice switch 5. Further, the privacy switch state storing circuit 8 outputs a signal that lights up a privacy telephone state indicating lamp 10 to inform a user of privacy telephone state. When a privacy switch is pressed to change from this state to speaking state and conversation is started, two-way speaking becomes possible until the interphone is made off or changed to privacy telephone state by pressing the privacy switch again. |
