| 摘要 |
PURPOSE:To prevent a leaked voice which occurred conventionally and cut off the transmission surely even if a user is at a distance from a telephone set, by giving a function, which generates an electric signal for cutting-off of the voice signal from a transmitter, and a holding function to an integrated circuit for telephone set. CONSTITUTION:When a push-button switch 14 or 15 is depressed in the call state, a high level is inputted to an AND gate 29 by a chattering eliminating circuit 27. When only one push-button is depressed, a transistor TR 3 is turned off to hold the transmission permission state; and only when two push-button switches 14 and 15 are depressed simultaneously, the TR 3 is turned on, and the generation of the voice signal is cut off, and the transmission is impossible while a telephone line is connected still. Though this state is held after push-button switches are turned off, an output Q of a flip flop 30 is inverted again to become low-level and the TR 3 is turned off to set the transmission permission state when push-button switches 14 and 15 are depressed simultaneously again. |
