Despite being from a 1969 publication, the transistors used have current equivalents such as BC548 and BC558. The circuit generates signals from 1 500 to 20 000 Hz and 4 scales.
This circuit, from a 1978 publication, uses a germanium power PNP, but the BD135 can be used for 6...
This two-tone buzzer can be powered by a solar panel. The circuit is from a 1991 documentation. The...
The SCR sector of this circuit can be powered by high voltage AC and instead of the LEDs we can...