System overview   
1.34  EST3 Installation and Service Manual 
Backup amplifiers 
Each cabinet can contain 1 zoned amplifier module to use to 
back up the remaining primary zoned amplifier modules installed 
in the same cabinet with the following restrictions: 
•  All the amplifiers must have the same output voltage rating. 
•  If the cabinet contains older amplifier modules (15- and 
30-watt) and newer amplifier modules (20- and 40-watt), the 
amplifier used to back up the primary amplifier modules 
must be of the older type. 
Note: In cases where older and newer zoned amplifiers exist in 
the same cabinet, the older modules should be replaced with 
newer modules for optimum results. 
•  The backup amplifier must have an output wattage rating 
equal to or greater than the largest primary amplifier it is 
backing up. If not, the output capacity of the speaker circuit 
is diminished proportionately. 
•  The wire used to wire the backup amplifier to the other 
amplifiers must be the same size or greater than that used to 
wire the speaker circuit. 
Cabinet space 
The 20- and 40-watt amplifiers each require one space on the rail 
assembly. The 95-watt amplifier requires two rail spaces. 
The number of zoned amplifier modules that can be installed in a 
single cabinet is limited by the number of available rail spaces, 
the number of power supplies installed in the cabinet, and battery 
limits, if any. 
Audio channels 
The EST3 audio system provides eight (8) simultaneous 
channels for distribution of audio signals. The functions of four 
of these channels are fixed by the system. These four channels 
are referred to by their functions: Page, EVAC, Alert, and 
Auxiliary Input channels. The four remaining channels are 
referred to as general channels 1 to 4. 
Under manual or automatic network control, each amplifier’s 
input can be connected to either the Alert channel, the 
Evacuation (EVAC) channel, the Page channel, the Auxiliary 
Input channel, or one of four (4) general input channels. Should 
conflicting commands be issued to a single amplifier, the 
amplifier responds to the channel with the highest priority. The 
eight channels are prioritized as follows, with the Page channel 
having the highest priority