CyberData paging system - need help getting working

Hello, I have a CyberData paging unit . [ http://www.cyberdata.net/products/voip/voip-loudspeakeramp.html
]
It is connected to our network at 192.168.1.75 . the speakers do work - pressing a button it speaks it’s i/p address.

I have an extension setup:
[150]
type=friend
secret=ext150
record_out=Adhoc
record_in=Adhoc
qualify=no
port=5060
pickupgroup=
nat=never
[email protected]
host=dynamic
dtmfmode=rfc2833
disallow=
dial=SIP/150
context=from-internal
canreinvite=no
callgroup=
callerid=device <150>
allow=
accountcode=

I’m using freepbx 2.3.0.2 & trixbox.

Could someone suggest what else needs to be done to set this unit up?

How does asterisk relate the i/p address to the extension?

I will post a how to when it is working.

thanks
Rob

Info: my asterisk computer i/p = 192.168.1.17
paging unit: 192.168.1.75

1- setup an extension:

[150]
type=friend
secret=ext150
record_out=Adhoc
record_in=Adhoc
qualify=no
port=5060
pickupgroup=
nat=never
[email protected]
host=dynamic
dtmfmode=rfc2833
disallow=
dial=SIP/150
context=from-internal
canreinvite=no
callgroup=
callerid=device <150>
allow=
accountcode=

2- setup the CyberData unit
The default address is on a 192.168.0 network.
Connect to it and change address to 192.168.1.75.

Change the SIP settings. have them match the extension.
http://192.168.1.75/cgi-bin/sipconfig.cgi

SIP Server: 192.168.1.17
SIP User ID: 150
Authenticate ID: 150
Authenticate Password: ext150
SIP Registration: Yes