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Introduction
Although primarily intended to assist the user of modern 16-mm. sound projection equipment, the simply-written contents of this book are so designed that users of all gauges of substandard and 16-mm. cine and "still" projectors will also find it of value.
The amount of time and care necessary to learn the correct methods for operating and servicing a 16-mm. sound projector, will, however, be considerably greater than with the smaller and relatively cheaper 8-mm. and 9.5-mm. models. The modern 16-mm. projector is expensive, and the post-war models are built to "professional specifications/ ' This means, briefly, that the user must now be taught a greater number of technicalities than was previously necessary, and the necessity for this injunction is at once painfully obvious when we consider that the cost of certain repairs to a 16-mm. projector may far exceed the purchasing price of a 9.5-mm projector. But are the instructions in this book so frightfully complicated? Not in the least — they are designed to inform the novice, and to guide the professional.
What then, you may ask, is the actual difference between these projectors of different gauge? In principle, there is no difference. All projectors have an optical system, an intermittent movement, feed and take-up systems, shutters, sprocketwheels, guide-rollers, etc., and the specific functions of these parts are the same irrespective of the size of the machine. The real difference is in the size, position, speed and relative efficiency of the parts. For instance, in a 9.5-mm. projector the teeth are positioned in a single row around the middle of the sprocketwheels, whilst in a 16-mm. silent machine the teeth are found on either edge of the wheels, and the latter may be larger and revolve at a different rate.
The intermittent movements may also vary, and the stop-andstart movement of the film may be accomplished by one of a number of distinctly different types of mechanism. But no matter what the mechanism employed, they all function to
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