Digital Knobs
Use this circuit to implement those knobs you see on oscilloscopes, radios and other devices. Turning the knob clockwise generates a series of low-going pulses from the COUNT-UP output while turning counter-clockwise generates a series of low-going pulses from the COUNT-DOWN output.
The circuit is based on a low cost Bourns digital encoder. Visit their page www.bourns.com , to see a complete selection of these devices.