Found in American documentation, this circuit can be used as a shield. The technology is CMOS and the input is BDC. Next to the diagram formulas for calculating the components.
This is an old test circuit for integrated TTL counters, feeding a Nixie tube, common at the time....
This old oscillator using germanium transistors has a high impedance headphone as inductor to...
This preamp with several inputs using germanium transistors from the time was found in Japanese...