215. General Description of the PG-10 Equipment. -The PG-10 equipment differs from the other SPU
equipments in several ways. The most noticeable of these is that no input control panel is used. The
volume control is mounted on the amplifier rack. The relay fader control and the exciter lamp rheostats
and ammeters are mounted on the projectors.
The PS-5, PS-6 or PS-8 sound heads are used with the PG-10 equipment, according to the make of
projector used. These sound heads are described in sections 97 and 98. The turntable used is the PT-7,
described in section 72. The amplifier rack furnished is the Type PA-21A, described below.
Only one voltage amplifier and one power amplifier is used with this equipment, as this equipment was
designed for the small theatre.
216. Description of the PA-21A Amplifier Rack Equipment. -Figure 125 shows a side view and Figure 126
shows a front view of the PA-21A amplifier rack equipment.
A type PA-12B voltage amplifier is used with this equipment and is mounted near the top of the rack.
This amplifier is slightly different from the voltage amplifiers used on other SPU equipments and is
described in section 139.
The type PK-1 power amplifier unit used with this equipment was described in section 140. This is the
same type of unit as is used on the other SPU equipments.
The compensator panel which is mounted near the top of the rack is of the same type as used on the
other equipments. The panel just below the compensator panel is the voltage amplifier control panel, and
the panel below the voltage amplifier control panel is the power amplifier control panel.
217. Description of the PA-21A Voltage Amplifier Control Panel. -The volume control, which is mounted
at the center of the voltage amplifier control panel, is similar to the volume control used on the PG-1
and PG-2 equipments and gives twenty steps of equal volume change.
Two indicator lamps, one on each side of the control knob, indicate which projector is "faded in" to the
voltage amplifier. The fader switch is relay-operated from controls on the projectors. The relay itself is
mounted on the rear of this panel and is readily accessible for cleaning by removing the left-hand side-cover of the rack.