I am the original owner. This is a great unit can be connected to a Midi sound module, Drum Machine, or your computer or phone with the right cable. I have done all except phone. I purchased this from American Musical Supply in the 90s. Used it for a few band rehearsals. I even have a perfect softcase for an extra $10. Unit runs off a boss or Ibanez footpedal power supply or 6xAA batteries.
Official descript
The Roland PK-5 (and later PK-5A) is a vintage out-of-production, 13-note velocity-sensitive MIDI bass pedalboard designed for hands-free performance. It allows musicians to control external MIDI sound modules, synths, or samplers, featuring four modes—Bass, Poly, Drums, and Sound Effects—spanning a nine-octave range, powered by an external AC adaptor.