System overview 
EST3 Installation and Service Manual  1.35 
Page channel 
Paging is a manual function. An operator is required to select a 
destination for the page, and then make an announcement. The 
Page channel is never automatically selected by the EST3 
system. 
The page channel always carries a live page signal, regardless of 
its source. There are three sources which can supply the paging 
signal: 1) the local 3-ASU microphone, 2) the remote 
microphone, and the 3) the firefighter telephone system. These 
sources are automatically prioritized as shown in Table 1-2. 
 
Table 1-2: Page priorities 
Priority  Page signal source 
1 (highest)  Local microphone  
2 Firefighter phone 
3 (lowest)  Remote microphone 
 
The page command is a non-latching function. When the page 
command ends, amplifiers automatically switch back to the 
source channel that was active (if any) prior to the page 
command. 
Five types of page commands are available on the network. The 
first four page commands are available simply by pressing a 
single switch on the front of the 3-ASU. These are the paging 
functions most commonly used in an emergency situation. 
1.  The All Call command temporarily transfers all amplifiers to 
the Page channel while the page is active. All Call distributes 
the page signal to every amplifier in the system. 
2.  The Page to EVAC command temporarily transfers the Page 
signal to all amplifiers actively connected to the EVAC 
channel. All “EVAC” amplifiers then receive and distribute 
the Page signal. 
3.  The Page to Alert command temporarily transfers the Page 
signal to all amplifiers actively connected to the Alert 
channel. All Alert amplifiers then receive and distribute the 
page signal. 
4.  The All Call Minus command temporarily transfers the page 
signal to all amplifiers except those connected to the EVAC 
and Alert channels. 
5.  A Selective Page temporarily transfers the selected 
amplifiers to the Page channel while the page is activate, 
distributing the page signal only to selected audio zones