upon a curved or concave screen rise from the floor when the picture is tilted, a bottom masking with a curved top is indicated for such tilted installations. However, since the public has been accustomed to the straight lines of present maskings and the curved masking presents several additional problems, the bottom masking may be installed level in most instances provided it does not mask essential portions of the center of the picture upon which it must encroach.

The side maskings should be adjustable in width, possibly with a stiffened leading edge - to close in to mask the sheet for conventional pictures, and to open up to mask the sheet for the CinemaScope picture.

This may be done by supporting the side masking on tracks with suitable stops on the tracks and at the floor, or by other means, as may be devised by the engineer or the purchaser.

For this purpose, and for the use of close-in curtains, curved tracks are available from the supplier.

In all cases a curtain, and including a valance, should be employed, if for no other reason than to keep the screen clean.

The curtain may be mounted on a curved or a straight track as may be indicated, and can be used for a side trim or false proscenium where required or desired, or extended with fixed tabs at each end to form a transition between picture and the house decoration.

The stereophonic sound system, basically an integral part of the CinemaScope system, consists of an element to be attached to the projection head at its intersection with the upper magazine, designed to pick up the magnetic tracks of the picture film, together with the necessary pre-amplifiers, matched amplifier and speaker assemblies with monitor and other associated equipment.

The operation of this element will be controlled by switching arrangements as will the photographic pick-up in the present sound head, permitting them to

operate independently of one another as desired.

Since, in addition to the three primary magnetic sound tracks required for stereophonic sound, CinemaScope picture film will be supplied with a fourth effects and control track, some theatres may wish at their own election to extend the range of participation or effect into the auditorium where an additional preamplifier and amplifier will be required, together with a number of house speakers as may be indicated by survey.

The Amplifiers: In every case, the amplifiers provided for stereophonic sound must match, but should the present amplifier be entirely suitable, it may be retained and two identical amplifiers added to complete the basic requirements of CinemaScope.

Should it be unsuitable, its use for auditorium speaker use should be assessed, and three perfectly matched units installed.

Speaker Assemblies: In every case, the speaker assemblies must match, but should the present speaker assembly be entirely suitable, it may be retained and two identical assemblies added to complete the basic requirements of CinemaScope.

Should the speaker assembly be unsuitable, then three matched units must be installed.

The suitability of the amplifiers and the speaker assemblies and the ability to match them must be determined by the equipment-supplying engineers after their survey of the theatre.

The three speaker assemblies will be mounted in the usual manner back of the screen, one upon the center line, the other two on the center line of each outside one-third of the picture, i.e., at W/3 each side of the center line and as close to the screen surface as practicable. Proper mounting is extremely important if the maximum effectiveness possible with stereophonic sound is to be attained throughout the theatre.

No braces or other obstructions in the frame construction should be permitted to be installed immediately in front of these assemblies.

For additional definition of W/3, consult the screen frame drawings included in this manual.