This circuit is from a Radio Electronics from October 1963. The transistor is a power transistor of the time, and two transformers are used. The input has 10k impedance and is powered by 12 V.
Found in a 1966 documentation, this “coin finder” uses components from the era operating at 2.1...
This filter operates in the “opposite” way to the previous one (CIR8814), cutting all signals...
In the figure we have the way to use a stepper motor as an encoder. Operational amplifiers can be of...