This circuit was obtained in a Popular Electronics from the 90's. The gain depends on R4 and R3. Transistors are general purpose types.
September 2017 - Mouser Electronics counts in stock with Murata Y1 ceramic capacitors for SMD...
This contact or reed switch actuation was found in a 1964 Electronic Design. The circuit can be...
This 1-transistor circuit for currents up to 50 mA was found in the August 1974 Radio Electronics...