This is a field strength meter found in an 80's Hands On. The circuit operates at frequencies up to 500 MHz and has a buzzer as its indicator. Can be used as a detector for spy transmitters.
In this circuit of a 1968 publication the unijunction may be 2N2646 and the transistor BC548. The...
The purpose of this circuit is to improve a trigger circuit using a zener diode. The circuit was...
This interesting circuit of the American publication Electronics Handbook Volume XIII 1993 shows a...