This circuit, found in 2002 documentation, triggers LEDs when a phone call is received. The LEDs will flash alternately in these conditions. Common LEDs are used in this circuit.
This two-transistor circuit is from a Radio Electronics magazine from April 1965. The transistors are...
This low power circuit for the FM band was found in a spy book from the 90s. The tunnel diode is...
We found this circuit in a Gernsback documentation from 1960. The circuit is intended for...