200. General Description of the PG-6 Equipment. -The PG-6 equipment is the largest of the partially SPU
operated equipments and is used in large theatres. It uses PS-1 sound heads and PT-2 turntables. Two
amplifier racks are used; one (Type PA-19A) contains two Type PA-12A voltage amplifier units, and
the other (Type PA-20A) contains four Type PK-1 power amplifier units. See sections 138 and 140. Only
one voltage amplifier unit is used at a time and the power amplifier units may be used individually in case of emergency. The volume control is mounted on the voltage amplifier rack instead of on the input control panel. This input control panel (the Type PA-16B) is described in section 110.
201. Description of the PA-19A Voltage Amplifier Rack. -Figure 121 shows the arrangement of parts on
the PA-19A voltage amplifier rack. The top panel is the compensator panel. The second panel from the
top is a metering panel. The third and fifth panels are alike and are voltage amplifier control panels, one
for each of the two separate voltage amplifier units. The fourth panel from the top is a switching panel
used for switching the input and filament supply from one voltage amplifier to the other. The two
voltage amplifier units are mounted in back of the five upper panels. The battery boxes for the amplifiers
are mounted in back of the two bottom panels.