Found in a 1969 EDN, this high current circuit, not indicated in the documentation, uses transistors from that time. The input voltage can be between 9 and 11 V.
This interesting capacitive water level sensor was found in Popular Electronics. The circuit can be...
Using transistors at the time, this circuit was found in a 1967 Ferranti documentation. The...
This circuit locks when the sensors are opened. The relay can be 6 or 12 V depending on the power...