With this circuit you can produce the sound effect passing from one channel to another. The circuit is from Mullard documentation from the 1960s. The transistors may be the BC548.
This conventional power supply circuit with the LM317 was found in a 1987 publication and its...
This circuit was found in an 80's EDN. The circuit uses a current common CMOS, the 4093 powering...
This detector is from the 1990 Motorola Dataar Databook, but can be adapted to work with more...