This circuit provides a reference voltage of 2.5 V adjusted in the trimpot. The transistor can be the BC558 (in the drawing it came out as NPN). The control is done by a rectangular input signal.
This small circuit for the medium or short-wave range, depending on the coil, was found in a...
Pressure switches are used in this circuit that quickly turns off the supply of a load if...
This circuit will trigger an audible warning signal after the end of the pre-programmed timing. Using...