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.
Also suitable for use as a noisy alarm, this Morse Code or telegraph practice oscillator was found...
The figure shows a white noise generator circuit that uses a transistor junction to generate the...
Flybacks are no longer misused. However, if the reader wants to recover an old analog television...