This SCR circuit is intended to control an AC load with a low current switch. This switch can be a reed sensor. The load depends on the SCR.
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...