In regard to the Pratt-Read tracking device, there is another of
these devices also put together by Pratt-Read which is a four-bellows
type unit.  This beast is one of the most complicated and thoroughly
useless pieces of junk that was ever dreamed up in some engineers
mind.  The single, under-the-spoolbox type is a breeze compared to
the four-bellows type, and it works considerably better.

Pratt-Read had some good ideas for much of their product line but
often as not there are real clinkers out there that should have been
re-thought.

Jim Jelinek