We found this circuit in a 70s RCA manual. The circuit uses an LDR by directly driving a sensitive relay. Resistor R1 is 5.6 ohms and R2 is 25k. The pot is 10k of wire.
Two identical transformers can be used as a single improvised isolation transformer. The maximum...
This transmitter can send its signals from several kilometers away, depending only on the antenna...
This circuit was found in Radio Electronics magazine from January 1959. The power transistor must...