Hi Fellow Travelers,  I want to thank those that responded to my
message regarding phase locked loops (PLLs). I apparently did not
clearly state my reason for the message.

My main intent was to have explained the particulars used to compare
the step size of any Ampico roll -- which could be elongated, shrunk,
warped, have slipped paper punched holes -- against the apparently
accepted standard of 356 punches per foot, the "intended" step.

That a type of PLL method was used is clear to me and if there was
some uncertainty in my mind what PLL meant in general, the responses
and e-mails I received have removed those last vestiges of doubt.

The process used by Mr. Stahnke appears to be that the "run of the
mill" production piano roll was run through a scanner, and a custom-
designed computer program (in QBASIC?) recorded all pertinent
perforation information.

This was then compared to the "intended" step information (356 steps
per foot) and corrected accordingly, if and when called for.  This would
be the referred-to "phase locked loop" process, if I correctly under-
stand the gist of the process.

The result would be a file containing all transcribed perforations and
spacings between perforations, spaced at exactly 356 steps per foot.
I would like to get a copy of those programs and if he reads this, my
e-mail address is at the top.

Albert de Boer

 [ Wayne began work on his computer programs in the 1970s, long
 [ before QBASIC became the versatile programming language it is
 [ today.  He writes for the MS-DOS operating system now using
 [ "C" programming language.  The heart of his process is the
 [ image recognition program routine which identifies the centers
 [ of the overlapping perforations, with 0.1 millimeter resolution.
 [ -- Robbie