In fact, this circuit from the 60's applies to photographic printers of the time, timing the lighting of a 20 W lamp. The components are from the period.
We found this circuit in a 1998 documentation. It tests common household appliances to see if they...
This circuit uses a triac to detect the level of a reservoir, and a sensitive SCR connected to the...
We found this circuit in an English publication from 1980. The transistor can be either the BC548...