This circuit reproduces the dial noise in a small speaker. The transistor can be a general-purpose type. We found it in an 80's Electronic Design.
The circuit shown in the figure uses a programmable unijunction transistor (PUT) of the BRY39 type...
This circuit was sent by reader and collaborator Adriano Muniz Moura from Pirapora – MG. The...
This remote control for resistive loads using a triac appears elsewhere on this site. The circuit...