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
(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.