This circuit was found in a Popular Electronics from the 90's. The components used are common and instead of the buzzer we can use an LED or a relay.
This circuit intermittently activates a relay. It was obtained in a 1980 publication. In fact, we...
Suggested by a Popular Electronics, this small amplifier that has a detector to follow RF...
This source gently applies the voltage to the load, causing it to rise slowly, thus avoiding...