This Schmitt optical trigger with LDR was found in old documentation. The relay must be sensitive, or an additional step must be used to trigger it.
This circuit was obtained from Dutch documentation from 1967. It uses transistors of the time...
This circuit was found in the RCA Power Transistor manual from the 70's. The circuit uses power...
This circuit is from a 1969 RE Experimenters Handbook. The circuit is powered by the voltage of the...