| 摘要 |
PURPOSE:To listen to surrounding sound even with a sound generator worn 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:When a sound receiver 1 picks up large sound, an output terminal of an inverter 11 goes to a H level and if no large sound is picked up at the sound receiver, since an input terminal of an inverter 46 of a signal changeover circuit 6 is at a L level, an audio electric signal input terminal and an audio electric signal output terminal are connected. When the input terminal of the inverter 46 is at the R level, the 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 an audio electric signal output terminal. Thus, a listener can notice a call even on the way of listening. |
