Hi,
I have one of these somewhere but not handy. I don't remember what
the deal is with the switch but I do recall that the one I bought had
the batteries taken out of it and replaced with a power supply.
I got the impression from the owner that the system originally
trickle-charged the batteries as the unit ran. Without the batteries
I think it would not work unless you take the back section apart and
rewire it.
It is _very_ nice early-PC machinismo. The quality of industrial
design put into the unit has rarely been matched. Back-lit display
and the whole deal.
I guess you could call it the DeLorean of early MS-DOS compatibles. :-)
Hope this helps...
Thomas