| 摘要 |
PURPOSE:To aviod the discontinuation of the reception voice caused by the noise squelch by carrying out the tone squelch action in preference to the noise squelch action. CONSTITUTION:In the state under which tone squelch circuit 1 is used, switch S is turned on by the mike hanger. Thus tone squelch IC1 operates, and the voltage is supplied to base side point C of switching transistor Q1. And transistor Q1 is turned off forcedly. In this case transistor Q1 is never turned on although the field intensity lowers with increment of the noise amount and the noise squelch is turned on with point G turned to 0V. With supply of the tone signal to input end (b), the rear-step switching circuit of IC1 is turned off. As a result, audio IC3 is turned on, and the reception signal supplied to audio signal input and (e) is amplified to be delivered through the speaker in the form of the voice. |
