This is a battery powered 3W power amplifier using germanium transistors. The circuit is from an English documentation from 1967. The transistors are from the time.
September 2016 - It can be obtained from Mouser Electronics modules with 2.4 inch from 4D Systems...
November 2016 - Ohmite resistive current sensor chips with resistances from 10 mΩ to 100 mΩ in SMD...
This simple circuit, which requires a low current (50mA) relay for 5 to 12V power supplies, was...