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.
What we have is a powerful flasher that can be powered by voltages of 12 V like the one obtained from...
A 0 V signal initiates sampling on this circuit suggested by documentation from the 1970s. The...
This circuit is used with low impedance microphones, such as small speakers, magnetic capsules of...