This circuit uses a transistor to trigger the alarm from a low quiescent current sensor. The relay is 12 V. The circuit is from Radio Electronics magazine, April 1975.
This 1960s Japanese commercial AM radio uses 6 germanium transistors and is powered by 4...
This well-designed bistable circuit was found in a 1970s documentation. Transistors can be current...
This microamplifier was found in a Popular Electronics from June 1968. It is an experimental...