> > > >

1945 Theatre Catalog, 4th Edition, Page 351 (327)

1945 Theatre Catalog, 4th Edition
1945 Theatre Catalog
1945 Theatre Catalog, 4th Edition, Page 351
Page 351

1945 Theatre Catalog, 4th Edition, Page 351

inside with %-inch cement or acoustical plaster.

Doors At each end of the projection room,

1 a door not leSS than 2 feet 6 inches wide

and 6 feet 8 inches high of the approved fire-door type, self-closing, and swinging outwardly, will provide the necessary means of egress and ingress and at the same time satisfactorily protect the balance of the theatre.

Should either projection-room door lead into the auditorium, it should be a double one, with at least a 2-foot air lock between, for added safety.


It is desirable to provide one or more windows in the rear wall of the projection room, if this wall is an exterior wall of the theatre. The window frome must be of steel construction and the glass of the shatter-proof type.


A11 porthole openings must be covered by gravity type shutters sliding in metal frames and constructed of not less than N0. 10egauge iron.

The drop shutter should overlap the openings at least 1 inch all around and should be connected to a system that will operate automatically in case of fire or other emergency. Fusible' links above each shutter and over each piece of equipment asures immediate system reaction to fire. Large porthole shutters should be counterweighted to facilitate manual operation.

Projection ports should be about 10 x 10 inches, masked after the machines are set and properly aligned on the screen to an area just a bit larger than that which is required to paSS the whole projected light beam. Observation ports should be large enough to give the projectionist a clear View of the screen. As a result, for easy viewing, these ports are wider than they are high, with 14 x 12 inches affording a fair average. When included in the design, the spot port should be 2% x 2 feet. The distance of the centers of the ports from the projection room fioor varies according to the angle of projection.


The efficient operation of all projection room equipment depends largely upon the electrical wiring to and in the projection room. This is especially true in regard to power wiring both of the primary and secondary (a.c. and d.c.) requirements.

The a.c. power wiring to the projection room location is generally for 3-phase, 208-250-volt, 60-cycle a.c. current which Supplies the motive power for directcurrent generators which, in turn supplies the d.c. power to the arc-lighting eQUiDment, or furnishes the primary excitation for the transformers of arc Supply rectifiers.

The a.c. power supply line should be of ample size and conductivity to furnish 311 Primary load requirements with at least a 25 percent over-load factor. If CODdPCtors are just large enough, or undemlled, the resultant IR drop in the line may seriously affect the operation of the motor-generator or rectifiers. This In turn will affect the automatic feed



controls of the arc lamps, poor screen illumination will result and the generator, or rectifier, may overheat to such a point as to become inoperative or be permanently injured.

The installation of any projection room

.equipment, the power requirement of

which is in eXCess of the power required on equipment which has been in operation, should not be assumed until a competant electrician has checked the power lines to determine if the new equipment will operate efficiently with existing wiring. If a re-wiring job is indicated, this should be done before the new equipment is installed, as it will provide greater economy and more efficient operation of the new installation by operating the component parts of the manufacturers specified ratings.

A constant voltage is one of the foremost requirements of modern projection room equipment. For instance, in the past few years, new and improved carbons have been developed using a low arc voltage and giving greater economy to the arc-ampere. Due to this low voltage requirement, the potential must be maintained accurately or impaired operation will result. The carbons will

not burn properly when the arc supply '

voltage fluctuates. This condition upsets the automatic arc control device causing poor feeding of carbons and unsteady screen illumination which, of course, is undesirable.

The foregoing is proof that it is highly necessary to have the proper Wiring in the projection room for optimum equipment efficiency.

Ordinary rubber-covered cord or wire should not be used Where it will be subjected to lubricating oil. Oil will, after a time, dissolve the rubber covering, causing a direct short circuit of such conductors. For such applications, a special hard-braid or varnish-coatedinsulated cord should be used.

All switches, switch cabinets, ballast rheostats, bus panels, and the like should be inspected regularly to make sure that

the contact and current-carrying parts are clean and that all connections are tight. If this is not done, normal vibrations may loosen a terminal unit, creating a high resistant contact which, in some cases, will burn completely away and stop the show before it is discovered.

Many cases of complaint as to the operation of arc lamps can be traced to a loose connection hidden away somewhere behind a switch or terminal panel. The trouble can be avoided by a regular system of inspection by the projectionist in charge of projection room maintenance.

Only the professional-type of projector shall be used in the theatre.

The definition of such projector is one that carries the approval of the National Board of Fire Underwriters and which uses 35-mm. film (which is 1% inches wide) with uniform perforations on each edge measuring 5.4 perforations to the inch.

Drive motors for professional type projectors shall be approved as to design and application. Such motors must be enclosed or otherwise guarded against any possibility of sparks or are from brushes or contactors coming in contact with film while threading projectors, rewinding film, or during any necessary handling of film in the projection room.

Conductors supplying outlets for professional-type projectors shall not be smaller than No. 8, A. W. G. standard. Any special application requiring larger conductors must be calculated with the full-load current as well as reasonable safety factor in carrying capacity above full-load requirements. Such factor is generally figured to be 25 percent. Asbestos-covered conductors shall be used on are lamp or other equipment where the ambient temperature at the conductor as installed will exceed 120 degrees Fahrenheit.

Any fiexible cords used for portable equipment in the projection room shall be of the hard service type, such as K, S, or SJ.


- 327
1945 Theatre Catalog, 4th Edition, Page 351