This circuit consists of a simple continuity test with two transistors forming a relaxation oscillator. The circuit is powered by 9 V battery or 4 small batteries and directly excites a small speaker.
![](/images/stories/cir/2061262023_140306_0001.jpg)
This circuit consists of a simple continuity test with two transistors forming a relaxation oscillator. The circuit is powered by 9 V battery or 4 small batteries and directly excites a small speaker.