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 the February 1970 issue of Radio Electronics Magazine. It uses an RCA...
This power source can supply currents in the range of 100 mA to 1 A, depending on the transformer and the...
This circuit consists of a constant current source for charging 12 V batteries. The charge is...