In the words of Source Audio:

The Source Audio Dual Expression Pedal delivers precision response and smooth action in a durable cast aluminum housing. Dual TRS expression outputs make it possible to control two effects units simultaneously. The pedal is compatible with the very common Boss/Roland style (tip hot) expression input. The Range Adjust Knob sets the bottom point of the expression range. Plus, a special Sensor Output connects directly to any Hot Hand, Soundblox, Soundblox 2, or Soundblox Pro pedal for real-time control over filter sweeps, effect modulation, LFO speeds, wet/dry mixes, drive levels and more.