Found in Popular Electronics from the 90s, this circuit mutes a scanner's speaker in the absence of a voice signal, thus eliminating the hiss.
This simple circuit was found in an English magazine that no longer exists, January 1970 issue. It is...
This circuit, suggested by a 1975 documentation, detects an electrical discharge in a storm by...
This circuit for timing small loads was found in a 1964 General Electric documentation....