This 4-tube circuit was found on a Radio Craft from December 1945. The circuit has excellent sensitivity. Power comes from a power supply with a transformer.
Found in Ferranti's 1968 documentation, this circuit uses a Darlington photo transistor to drive a...
Found in documentation from the 70s, this circuit uses components from that time. Some of these...
This circuit monitors the state of a 12 V battery and can be used directly with one, or even in a...