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by the pictures corresponding to the optical
track were optically reduced on to the print This resulted in a 16 mm film which carried
stock but each successive picture frame was two reels of 35 mm film and sound with the
printed on to every other frame on the 16 mm pictures interlaced and upside down with re-
film. The process was then repeated for a sec- spect to each other. On projection, after running
ond reel of 35 mm film whereby the other 3 mm the film through it was not rewound but trans-
track on the 16 mm film received the second 35 ferred from the take-up to the feed spool and
mm track and then the pictures of the second 35 run through the projector a second time when
mm reel were printed into the frames spaces left the second reel of film with its associated sound
blank by the first run. track would be reproduced.

To achieve this a special Harper projector was
designed and made using many of the same
components, e.g. sprockets and feed rollers as
were used in the printer, but no comprehensive
details are included in the Patent Specification,
only a general mention.
The equipment was designed and made in a
research department of Miles Aircraft under the
overall direction of Mr. F. G. Miles. The devel-
opment and constructional aspects were direct-
ed throughout by Mr. K. W. Hole. Ref 4.

Ref 4. shows an illustration of a three quarter
front view of the Harper 16mm S.O.F projec-
tor. Not surprisingly it bears a close resem-
blance to the larger semi-professional machines
of the later 1930s with a rectangular cabinet
containing the lamphouse and mechanism with
the feed and take up arms and reels on the top.
Ref. 4 states that the projector would also ac-
commodate normal 16mm S.O.F. prints but no
specific details are given as to how this was
achieved, except for mention of a small "fric-
tion sprocket" driven by the film fitted to the
projector about 3 inches below the gate to allow
for the difference in spacing between sound and
picture on 35 mm films as opposed to the spac-
ing on normal 16mm prints. A switched speed
control would also have been necessary but this
is not mentioned. A Maltese cross and sprocket
provided the intermittent motion to minimise
wear on the film. A 14 watt amplifier was built
into the base of the projector but could be
detached as a complete assembly if necessary.
It was claimed, Ref. 4, that the undistorted
volume produced from the individual loud-
speakers was sufficient to fill a hall with about
five to six hundred people present! This claim

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