This fuzz effect for guitars was found in an American 1980s documentation. The transistors may be the BC549 and should be battery powered for noise sensitivity. Diodes are commonly used.
This encoded lock circuit with alarm for use in homes was found in a publication from the 90s. The...
This old circuit, from a 1992 documentation, was used with tape recorders acting as playback. The...
This circuit was found in a 1968 Motorola documentation. The circuit can be implemented with...