| 摘要 |
PURPOSE:To listen to surround sound even with a sound generator worm on the ear by using a signal changeover circuit to switch an audio electric signal and a signal from a sound electric signal source. CONSTITUTION:If a sound receiver 1 picks up large sound, an output terminal of an inverter 11 goes to a H level and if a sound receiver 1 does not pick up large sound, since an input terminal of an inverter 46 of the signal changeover circuit 6 is at a L level, the audio electric signal input terminal and the audio electric signal output terminal are connected. In case of the input terminal of an inverter 46 at the H level, an analog switch circuit 47 is connected and the oscillation signal of the circuit comprising inverters 7-10 of the sound electric signal source 5 is amplified by a transistor 27 and outputted at the audio electric signal output terminal. Thus, even with the sound generator 50 worm on the ear, connected to the audio electric signal output terminal, a listener can notify a call on the way of music listening. |
