Found in a 90s Electronic Design, this circuit is used with a 9 V adapter for powering small circuits. The maximum current is given by the 250-mW regulator.
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...