System information

is connected to a paging interface such as a Bogen UTI1,
§
which then connects to the
paging amplifier.
‖
In your dialplan, paging to an external amplifier would look like a simple Dial() to the
device that is connected to the paging equipment. For example, if you had an ATA
configured in sip.conf as [PagingATA], and you plugged the ATA into a Bogen UTI1,
you would perform paging by dialing:
exten => *724,1,Verbose(2,Paging to external amplifier) ; note the '*' in the
; extension is part of
; what you actually dial
same => n,Set(PageDevice=SIP/PagingATA)
same => n,Page(${PageDevice},i,120)
Note that for this to work you will have had to register your ATA as a SIP device under
sip.conf, and in this case we named the device [PagingATA]. You can name this device
anything you want (for example, we often use the MAC address as the name of a SIP
device), but for anything that is not a user telephone, it can be helpful to use a name
that makes it stand out from other devices.
If you had an FXS card in your system and you connected the UTI1 to that, you would
Dial() to the channel for that FXS port instead:
same => n,Dial(DAHDI/25)
The UTI1 answers the call and opens a channel to the paging system; you then make
your announcement and hang up.
Set paging
Set-based paging first became popular in key telephone systems, where the speakers of
the office telephones are used as a poor-man’s public address system. Most SIP tele-
phones have the ability to auto-answer a call on handsfree, which accomplishes what
is required on a per-telephone basis. In addition to this, however, it is necessary to pass
the audio to more than one set at the same time. Asterisk uses its built-in conferencing
engine to handle the under-the-hood details. You use the Page() application to make
it happen.
Like Dial(), the Page() application can handle several channels. Since you will generally
want Page() to signal several sets at once (perhaps even all the sets on your system) you
may end up with lengthy device strings that look something like this:
Page(SIP/SET1&SIP/SET2&SIP/SET3&SIP/SET4&SIP/SET5&SIP/SET6&SIP/SET7&...
§ The Bogen UTI1 is useful because it can handle all manner of different kinds of incoming and outgoing
connections, which pretty nearly guarantees that you’ll be able to painlessly connect your telephone system
to any sort of external paging equipment, no matter how old or obscure.
‖ In this book we’re assuming that the external paging equipment is already installed and was working with
the old phone system.
Overhead and “Underchin” Paging (a.k.a. Public Address) | 231