194. General Description of the PGA Equipment. -The PG-4 equipment is designed for small or medium
sized theatres. Like the PG-3 it has a separate input control panel which is usually mounted between the
two projectors. The equipment uses one Type PA-18A amplifier rack which consists of one Type PA-12A amplifier (see section 138) and one Type PK-1 power amplifier (see section 140). Except that only one voltage amplifier unit and
one power amplifier unit is used, the PG-4 equipment is very similar to the PG-3.
195. General Description of the PA-18A Amplifier Rack. -Figure 120 shows the arrangement of the parts
of the PA-18A amplifier rack. The second panel from the top is the compensator panel with the
compensator control knob. The voltage amplifier unit is mounted back of this panel. The panel below
the compensator panel is the voltage amplifier control panel. This panel is very similar to the PA-17A
voltage amplifier control panel except that fewer parts are used. The panel next to the bottom is the
power amplifier control panel. The battery box (only one is used with
this equipment) is mounted to the rear and a little above the power amplifier control panel. The power
amplifier unit is mounted back of the bottom panel.