This TTL circuit was found in the December 1990 issue of Radio Electronics magazine. The circuit has a 50% duty cycle. It must be powered by 5 V.
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...