We found this circuit in the 1964 RCA transistors manual. The sensor may be a common LDR and the transistor BC558. The relay has an operating voltage according to the power supply.
This circuit is based on the LT1004, LT1167, LT307 or LT1490 from Analog Devices. The circuit was...
This circuit, indicated by Texas Instruments, uses a high voltage regulator and a Darlington also...
This circuit is suggested by Texas Instruments and can be used on an assembly line to drive an...