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 can be used in decoration or to draw attention, in a “fake” assembly for example. What he...
This filter was found in Exar documentation from the 1980s. The circuit has an attenuation of 60 dB at the...
This windshield wiper timer was obtained in an 80's Hands On. The transistor can be the BC548 and...