This circuit is from 1999 documentation. However, it can still be easily assembled, as all components used are common. The sensors can have their quantity increased, being connected in parallel.
This transmitter for the 40 meter or 7 MHz band was found in a magazine 73 for radio amateurs of...
This sinusoidal oscillator was found in Radio Electronics in 1989. It uses a 741, but other...
This circuit changes the actuation curve of a 47k or 50k linear potentiometer so that it becomes...