International Review of Educational Cinematography (Jan-Dec 1932)

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Technical Notes THE NEW WESTERN ELECTRIC SOUND APPARATUS FOR 16 mm FILMS The Western Electric Co. has decided to offer its own interesting contribution to the practical solution of the problem of the reduced size sound film for family, amateur and cultural propaganda purposes. It has chosen, naturally enough, the sub-standard size, but has used instead of a photoacoustic system a gramophone synchronizing system, with discs giving 33 and 1/3 turns a minute. The new sound projector is easily portable. With the exception of a screen the whole apparatus can be packed into two suit-cases, one of which contains the projector itself with disc support, while the other carries the loud-speaker and the amplifiers. Aluminium has been used as much as possible in order to make the apparatus as light and easily portable as possible. The head of the projector is mounted on a moveable support which is capable of giving the optical projection axis a positive elevation of 15 degrees, and a negative one up to 5 degrees. The projector has two lenses. At a distance of 12 metres, it can give a perfectly luminous image measuring 1 .80 metres by 1 .50. The illumination is supplied by a normal projector lamp. A voltmeter allows the tension of the lighting circuit to be controlled. Moreover, a variable resistance permits of compensating possible oscillations in the light supply. The apparatus is furnished with a ventilation system in order to prevent excessive heating of the film and to allow fixed projections be shown with it. The small turbine which creates the current of ventilation is worked by a perfectly silent motor which does not in the least disturb the acoustic reproduction. The motor of the projector which also works the disc support plate is of the induction type of 1 /20 HP with a speed variable from 3540 to 3560 turns a minute. Between the motor and the apparatus a friction coupler has been introduced in order to take up the shocks due to starting the machine. As soon as the machine has reached its normal velocity, the friction coupling ceases to work, except in the case of excessive resistances being present, when the device helps to preserve the machinery from abnormal strains, which might cause a breakdown . Both the mechanical and the electrical parts of the apparatus have been devised so as to prevent the working of the machinery in any way disturbing the acoustic reproduction. The machine is therefore perfectly silent, a vital necessity for a projector which is intended to operate not in a closed cabin but in the same room with the audience. Even the elctric motors have been chosen so as not to cause disturbance in the amplifying circuits. The motor is mounted on four supports consisting of four adjustable springs which determine its vertical position and on four rubber discs which fix the horizontal position. The lay-out of the various parts of the disc-carrier is most interesting. The track which is very short is worked by the motor with a reducing gear on an endless thread. Beneath the intented wheel which turns the axis of the system there is a compressed felt cylinder, the dimension and the