This audio oscillator is from a 1957 Raytheon publication. The tone generated depends on C2 and C2 and the handset must be high-impedance magnetic. Equivalent transistors can be tested.
Found in an Elektor from the 90s, this circuit simulates a rotary switch that provides a BCD...
This crystal shortwave radio can tune signals up to the VHF range of analog TV (which no longer...
This circuit was found in a 1987 edition of the United States' Hands On Electronics magazine. The...