This circuit has a correction or linearity adjustment. We found it in Ferranti's transistor manual from 1974. Transistors are general-purpose types at the time.
This 1kHz rejector filter can be modified to operate at other frequencies. Operational can be just...
This small audio amplifier is based on the LM390 with a minimum of external components. We found it...
We found this circuit in the Audio Handbook of the National Semiconductor of 1977. The circuit is used...