My boss picked up this multiplexer from eBay. On the front it says QK 4 Plex. On the bottom, the sticker says it's a Model DM/QKX1/S/N/C/M.

The power plug on the back is an 8-pin mini-DIN. This is what we're looking for- either a power supply for it, or the specs on the pin-out.

Yeah yeah, we'll probably call up Dedicated Micros anyway.. but I figured someone here might have something useful to share.