本文所要介绍的这种双音电子喇叭,具有电路新颖、制作容易,调整方便,体积小巧等特点。它可以用作各种玩具的音响源,也可以用它制作各种音响报警器。电路原理双音电子喇叭的电路见图l所示。它由两只NPN型和一只PNP型硅晶体管组成直耦式互补低频放大电路。笔者巧妙地在晶体管BG_1的基极与BG_2的集 This article should introduce the dual-tone electronic speakers, with novel circuit, easy to make, easy to adjust, small size and so on. It can be used as a sound source for a variety of toys, you can also use it to make a variety of audio alarm. Circuit Two-tone electronic speaker circuit shown in Figure l. It consists of two NPN-type and a PNP-type silicon transistor composed of direct-coupled complementary low-frequency amplifier. The author skillfully sets the base of transistor BG_1 with BG_2