Found in a 90s Elektor, this mixer makes use of integrated circuits of the time. The supply must be symmetrical at 15 V.
This 1975 circuit for automotive applications replaces the mechanical vibrator found in old cars...
The transistors in this circuit, found in an American publication in 1975, can be replaced by...
This inverter amplifier is from a 1992 publication. NPN transistors can be BC548 and PNP BC558....