I appreciate John Tuttle posting the illustration from the Duo-Art
service manual detailing the (typical) tracking system [180810 MMD].
I was on vacation and away from my reference materials when I wrote
my adjustment procedure a few days before.  But it's apropos to the
discussion for a couple of reasons:

1. It shows the internal bleeds in the branched supply line that go
into tracker pneumatics.

2. While not specifically mentioned, the careful observer will deduce
that if there is enough leakage to atmosphere, from either pneumatic,
that is more than the air passed through the bleed, then the pneumatic
will simply not move.

3. This places an extra burden on the restorer to use good recovering
techniques to avoid any leakage at the various corners.

4. It also amplifies the need to use the very best airtight materials.
Low-quality, porous materials can easily "overload" the bleed(s) and
render the tracker inoperative.

5. Although the diagram doesn't actually show the connection of the
supply line to a constant vacuum source, it should be obvious that such
is the case.  The tracker _must_ be under power during rewind, but it
_must not_ receive any correction signals from the tracker ears during
rewind.  It is the function of the cut-out block to make sure that
doesn't happen, but any (signal) leakage up to the point those tubes
enter the bottom of the tracker pneumatics will compromise the
operation.

John Grant