This simple circuit for headphones or small speakers was found in documentation from the 90s. The circuit works with voltages from 5 to 9 V and has good gain.
This circuit, which can be used as a shield, was found in American documentation from the 1970s....
This circuit for low frequency data transmission was found in the May 1977 issue of Radio...
This circuit activates a relay that has a lamp as a load. The circuit is from a Radio Electronics from...