The transistors of this circuit found in an English 1980s documentation may be the modern BC548 equivalents. The circuit is battery powered and the earphone must be crystal.
This stage circuitry for amplifying microphone signals makes use of germanium transistors as indicated...
This low power audio amplifier was found at 1992s Popular Electronics. Transistors are general...
This Phase-Shift Oscillator produces sine low frequency signals suitable for many applications. It...