Found in Philips' 1967 documentation, this circuit makes use of period components. The SCR can be of any type, depending on the power of the controlled load.
We found this circuit in a European publication from the 1970s. The transistors are made of...
The TAA131 used in this circuit is not very easy to find today, but an equivalent low power audio...
This circuit was suggested by National Semiconductor in its Linear Application Handbook. The...