This approach alarm circuit was found in the September 1970 Radio Electronics issue. The 1 mH coil is wound on a ferrite rod. The relay is 12 V sensitive.
This is the traditional configuration of an inverter amplifier with operational. The operational...
In the figure we show how to implement a voltage-controlled oscillator. The circuit is from Texas...
Found in a 1967 American publication, this circuit with feedback for two transistors has a gain of...