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 from 1964 documentation but can be easily implemented based on current components....
This circuit, which can generate voltages up to 25 V, was found in the December 1992 issue of...
Found in National Semiconductor documentation from the 90's, this circuit has an output current of...