This sensitive touch key appears on this website from other sources. This version was taken from a 90s American documentation. The source must not be of transformerless type.
The circuit shown in the figure uses a programmable unijunction transistor (PUT) of the BRY39 type...
This circuit generates a 5V rectangular signal. The circuit is suitable for calibrating TTL...
This configuration, explored in other applications of this section and website, was found in a 90s...