This circuit for very low frequencies was found in an American documentation from the 90's. Transistors are for general use and the frequency depends on C1 and C2.
This circuit uses a 4 ½-digit indicator of the type TIL33oA (1 unit) and TIL321A (4 units). Driver...
The circuit shown consists of a NO and NC sensor system for alarms. The output must be connected to a...
From a 90s Popular Electronics, this circuit emits pulsating signals for different types of...