AUTOMATIC TALK LINE DEVICE

摘要

PURPOSE:To deliver automatically an external sound signal supplied from a built-in microphone to a headphone, by discriminating the level of the external sound signal. CONSTITUTION:A built-in microphone 15 can collect external voices while a headphone 14 for reproduction of a main sound signal. The output of the microphone 15 is fed to a level discriminating circuit 17 via an amplifier 16 as well as to an amplifier 12 via a talk line circuit 18. The circuit 18 is disconnected and an attenuator circuit 11 is inactive when no external sound signal exists. Then the reproduced output signal given from a reproducing head 10 is supplied to the headphone 14 via amplifiers 12 and 13. When the external sound signal exceeds a prescribed level, the circuit 17 is actuated to invert a switching circuit 19. Thus the circuit 18 is connected. Then the external sound signal supplied from the microphone 15 is supplied automatically to the head 14.