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.
The improvement we found in this stage on a common basis is the use of only one power supply. The...
This SCR circuit, which can also be used for signaling places, was found in old American...
This circuit, which appears from other sources on this site, converts a voltage into a current....