Strange box

Hi, I found this in a pile of surplus computers yesterday. Can anyone tell me what it is? It looks like an ordinary external 5 1/4" drive box but on the back of the box it has a DB-25M connector marked "MODEM/CPU" and a DB-25F connector marked "TERMINAL". There's also a rotary switch labeled "RATE" with positions marked "10", "30", "120", "240", "480", 960" and "EXT". Then there's a toggle switch with positions marked "BIN CTRL ON" "ODD" and "EVEN". And another toggle switch with positons marked "FULL" and "HALF". It has a socket for a standard AC line cord. It's made by Techtran Industries of Rochester, N.Y. and it's a model 950A. My guess is that it's a disk drive that's made to go between a terminal and it's MODEM or computer but I've never heard of one before. If that's what it is, then how do you give it coomands? Joe