image from a Sequential Circuits ad featuring the Prophet Remote (courtesy of Benjamin Ward)
The Sequential Circuits Remote Prophet was designed to be a remote keyboard for the Prophet-5. It came with a 20 foot long cable and its own guitar strap. To the left of the 4-octave, 49-note (C-C) keyboard is a control arm containing wheels for pitch-bend, modulation amount, and a third which was switchable between volume and filter cut-off. Above the keyboard are the program switches, five bank buttons and eight program number buttons, each with their own LED for instant recognition of what program has been selected. The cable carries power to the Remote from the Prophet-5 and carries a digital signal back to the Prophet-5. It speaks a serial protocol which could be considered a primitive version of MIDI (then not yet developed). Unfortunately, for Sequential, the Remote did not sell very well. Though it weighed less than 5kg, it just didn't have the looks that made people want to strap it on and parade around stage with it.
[from The A-Z of Analogue Synthesizers, by Peter Forrest, published by Susurreal Publishing, Devon, England, copyright 1994 Peter Forrest]