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.
This small transmitter with 2 transistors can reach several hundred meters using a 30 to 70 cm...
Built-in Littelfuse itself This SiC N Channel MOSFET for 1200 V can be obtained from Mouser...
This source draws a fixed constant current of 1 mA using a Norton operational amplifier. Other...