This circuit is from an article that teaches how to assemble it in the magazine Electronics Now from July 1993. It uses a liquid crystal display module from the time with 3 and a half digits.
This repellent operates with frequencies from 30 to 45 kHz, serving for insects and rodents. The...
This circuit is from a publication from the 70s. The original text was kept. The medium...
We found this circuit in an old American publication. The transistors can be BC558 and diode 1N34....