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.
We found this circuit in a 90's EDN. The circuit is based on a control integrated that is still...
This circuit is based on a Texas LinMOS integrated circuit that consists of an operational...
This circuit, when connected to the 110 V power grid makes it possible to test capacitors with...