This powerful sound emitter used in defense to intimidate people was found in a 90s Popular Electronics. The circuit produces a strong modulated tone of 3 kHz. The modulation is 10 Hz.
This simple 1 transistor circuit was found in an American documentation from the 60's. The...
Found in a magazine 73 for radio amateurs, this circuit makes use of general purpose transistors and...
The presented circuit allows to control the valve of a tap. The positioning of the emitter and the...