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 circuit generates signals with two waveforms. The circuit is from a documentation from the...
This circuit was found in an 80's Radio Electronics. The circuit multiplies the frequency of a low...
Found in Electronics Now from the 1980s, this amplifier can also be seen in commercial amplifiers...