This 1968 Texas Instruments circuit uses diacs of the era. SCRs can be modern equivalents according to the controlled load.
We found this touch control on a Popular Electronics from 1970. The circuit makes use of an...
This very low frequency circuit was found in a 1964 Electronic Design. Transistors may be modern...
This circuit, from the 1990 Motorola Dataar Databook, can be implemented with other comparators. The...