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.
Although not using transformers, this amplifier may have difficulty mounting if the original...
This flip-flop or bistable multivibrator is triggered by a signal applied to the base of the...
The integrated circuit used in this regulator is not very common today. The circuit is from old...