image courtesy of Kevin Lightner
Digisound sold their modular kits in magazines in the early 80's. They used mini-jack patch cords and their control voltage was set up as 1 volt/octave, which made them easily interfaced with most MIDI/CV converters. Their modules were 9 inches tall and between 3 and 9 inches wide.
[from The A-Z of Analogue Synthesizers, by Peter Forrest, published by Susurreal Publishing, Devon, England, copyright 1994 Peter Forrest]