Alarm with NC sensors (CB25946E)

This circuit was found in the Radio Electronics magazine of May 1990. The supply voltage depends on the relay and more sensors can be used.

Gain 1000 Sample and Hold (CB5960E)
This 80's circuit has been winning. It is a 1 000 gain sample and hold circuit and an offset...
Instrumentation Amplifier (CB4230E)
The purpose of this 1-transistor amplifier is to allow the use of a milliammeter in an application...
20 kHz ring counter (CB6138E)
We found this circuit in an old General Electric documentation. In fact, PUTs are not common...