This simple circuit for switching RF signals was found in an RF Design from the 90s. The circuit operates from 10 to 1 000 MHz and is 50 dB insulated.
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...