The circuit transistors, found in a 1974 documentation, may be the BC548. The circuit is used in quadriphonic systems to combine signals.
Other operational amplifiers can be used on this unit gain amplifier. The circuit is from the 1993...
January 2017 - Pulse Electronics ER11 transformers with high insulation can be obtained from...
This circuit was found in a 90’s Electronic Engineering. The integrated circuits are of the time...