It use to be the DMS-100 was a "local" switch only, the DMS-200 was
a "toll" switch only, and the DMS-250 was a combined "local & toll"
switch, all based on the same hardware design. Upgrading from a
-100 to a -250 was essentially a software upgrade (plus trunks).
The DMS-10 hardware/software was not based on the same design as
the -100. For all practical purposes, only the color of the paint
is the same. Don't know this for a fact, but would suspect there
are more common things between the SL1 PBX and the -10.