This receiver was found in a Popular Electronics from the 90's. Its different configuration shows a tuning circuit after the tube that works as an aperiodic amplifier. Observe supply voltages.
This simple oscillator with just one transistor has a frequency determined by the characteristics of the...
This Zero Crossing Detector was found in a 1972 RCA manual, but it can be made using any modern...
The circuit shown was found in a Japanese publication from the 1960s. Transistors can be...