These panels consist of an iron box 15 by 18 inches and 5 inches deep. This is mounted on the front wall of the projection room, between the projectors and about 4 f eet from the floor. In it are mounted the following:

(a) Two Exciter Lamp Rheostats and Ammeters, one for each projector.
(b) Potentiometer fader.
(c) Two five-prong input plug receptacles.
(d) Volume control. (On PG-3 and 4 equipments only.)
(e) Volume indicator milliammeter.

The two rheostats, labelled "Film Lamp-Projector A" and "Film Lamp-Projector B," control the current flowing through the exciter, or film, lamps. This current is indicated on the ammeter immediately above the rheostat knob.

The volume indicator is merely a delicate ammeter which moves back and forth as the sound input varies the amount of current flowing into the amplifier. This meter should never be allowed to read more than 0.85. This point is indicated on most equipments by a red line on the meter. It should never be necessary to run the equipment anywhere near that output.

The five-prong plugs which go into the receptacles on the input panel are removable. In this way it is made possible to use more than two projectors from the same input panel. In some cases where no more than two projectors will ever be used the input circuits have been wired permanently into the panel by means of conduit.

111. Input Controls Mounted on Projectors.-In types PG-10 and 13 equipments there is no input control panel as such, the various rheostats and meters being placed on other units of the equipment.

In Types PG-10 and 13 the exciter lamp rheostat and ammeter, as well as the "Film-Disc" switch, are mounted on the sound head as shown in Figure 75. The volume control is mounted on the amplifier and the fader is of the relay type. The relay is actuated by a switch, usually mounted on the projector under the lamp house or on the front wall of the booth.

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