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.
The presented circuit uses a symmetrical power source to supply an amplifier with the LM139 or...
This circuit was obtained from the 1995 Encyclopedia of Electronic Circuits Volume 5. The circuit...
The circuit shown is from the 1994 Linear Applications Handbook by National Semiconductor. Some of...