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 uses one of the first comercial transistor and is from a 1958’s magazine. Tone...
This circuit is intended to indicate the operation of transmitters with powers above 5 W. The...
Emitt This crystal-controlled oscillator can generate signals from 100 kHz to over 30MHz. The...