Published by Philips in 1965 documentation, the sensor for this circuit is a common LDR. The transistors are general-purpose types from the time, only TR3 is a power type according to the load.
This circuit was designed to power the previous circuits of the wireless sound system, but it can...
This circuit is from the documentation of Radio Shack 1975. It can be mounted with 12 V relays,...
This circuit is suggested by the Optoelectronics Sourcebook by Texas Instruments when AC signals...