Regarding John Tuttle's question about the Ampico (Automatic) switch
in the Ampico "A" [240610 MMD]: In my Ampico (which is from 1926,
so the most common model), the Ampico switch in the drawer has only
one tube connected to it.

The connection is open to atmosphere when the switch is in the
"Off" position and closed when in the "Ampico" position. The tube
is connected to the "Automatic Cut-Out" valve block, which is a
primary-style "outside" valve (so, atmosphere in = atmosphere out).

The output from this valve is tubed to the expression cut-out block.
So the expression block gets vacuum when the drawer switch is in the
"Ampico" position.

Bill Luecht