Found in Popular Electronics from the 90s, this circuit is based on a PLL567 and employs high-end or ultrasonic speakers depending on the frequency of oscillations.
The S-meter is signal strength meter, coupled to telecommunications receivers to indicate the...
This circuit is suggested by Motorola, making it possible to use an optical coupler of type 4N26...
Dynamic analyzer is another name given to a signal follower or signal chaser. This circuit is from...