This circuit was found I a 1965 Radio Schack documentation. The transistors are from that time, admitting equivalents. The transformer has 500 ohm primary and secondary depending on the speaker.
The circuit presented is from a 2006 documentation. It can turn a set of lamps on or off when...
This second-order filter was found in a 1978 publication and can use common operational amplifiers like...
This simple tone control using two transistors was found in an Electronics Today International of the 90s....