This circuit is from Motorola's Linear Databook from 1990. The integrated circuit and transistors are uncommon, but the circuit can be assembled with equivalents.
This circuit triggers a relay when the detected humidity falls below a value. The system can be...
We found this circuit in an old General Electric documentation. In fact, PUTs are not common...
This alarm circuit was found in a 1997 publication. It uses two reed-switches to arm and disarm the...