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.
We found this CMOS circuit in a 1978 publication. It allows you to use a standard calculator...
This circuit was found in a 1960s book of projects by Gernsbak. The circuit uses germanium...
This circuit was found in a 1985 documentation. It provides an audiovisual indication of the...