We found this circuit in a Radio Electronics from February 1966. The transistor is from the time and so are the transformers. The circuit is battery powered. Observe the impedances.
We found this source with the CI 723, common at the time, in a 1989 paper. Power transistors must be...
This old voice circuit suitable for telephones of the time was found in a Radio Electronics from...
We found this frequency meter circuit in a 1974 documentation. The circuit is powered by 12 V and...