From: Patent Tactics, George Brock-Nannestad
Hello, Bob Hodge wrote re catching up with missing film frames in a sound-on-
disc projection system so that lip sync could be maintained:
> The method of retard or advance was a special mount that allowed the tonearm
> to be advanced or retarded while the record continued at a constant speed.
> The tonearm mount rotates on a portion of the support column below the
> turntable gearbox.
> Darned clever those WE engineers!
----- yup, you could say that. However, a bit of calculation demonstrates
that there is a limit to the total number of frames for a whole reel that
could be corrected.
The records ran at 33 1/3 rpm, which calculates to 200 degrees per second.
This corresponds to 24 frames. This means that you have to move the pivot of
the tonearm 8.33 degrees for each frame lost, or a right angle (give or take)
for 11 frames lost. If the WE equipment was good and the film reasonable I
suppose this never happened. So, we may conclude that if the tonearm mount
was swivelable over a right angle they would be home free. However, the
differential that was used by other makers was continuously variable and did
not have to be reset when a new reel (corresponding to a new disc) was