The serial bus I/O SwitchBox. It is used to select which computer has access to which drives, and which printer.
The shorter serial cables are for drives. The longer serial cable is for a computer.
The red/black wire is the 12V supply line.
The rotary switches select the drives; device 8, and 9. The red toggle switch selects which computer has access to the drives. The left hand white toggle engages or disengages the reset line. With the reset line toggled out, I can reset the computer without disturbing the drives. Then I can read the error channel from the drive. The right hand white toggle selects between two printers.
In the center of the case are two 12 volt relays, that switch all the lines on the serial bus between the two computers. The rotary switches select the drives. The case was leftover from the Dual 1581 project.
A little different view.
A view of the rear. Here the two printers attach, as well as the second computer.