This static switch circuit appears elsewhere on this site from other sources. This was obtained from a Motorola documentation for 1968 power circuits. The Triac can be another according to the load.
This circuit detects light variations using two LDRs as sensors. Operational amplifiers and...
The circuit shown consists of a power stage for relay excitation. 2N3053 can be a BD135 and 2N406...
This circuit was found in Mullard's 1960s transistor manual. The circuit uses germanium...