Setting up FXS gateway (Grandstream HT503 or Obihai 212) to interface Valcom paging system

I am the IT admin for a private K12 school. We recently lost our old ESI phone system and I have been installing Asterisk based systems for over 10 year, so talked the school admins into letting me install the system to replace the ESI. Long story short, I have a new install running on a SIP trunk with 50 Grandstream phones. No issues with phones, users, VM, routing, etc… phone system is running perfectly.

The issue lies in the connection to my Valcom paging system. The Valcom system has a 2 wire interface for accept a call-in for the paging number. For instance, the old system would take the users input of 76208 and open the line to the Valcom 2924 and send 208 to it. Valcom has instructed me to connect a FXS gateway to the 2 wire input on the unit and set it up as a trunk.

So far, I have set up the HT503 FXS port with a username and password (using 701). I created a SIP trunk as below:

Trunk name: 701
Hide Caller ID
Max Channels 1

SIP Settings:
secret=xxxxxxxxxxxxxxxxxxxxxxxxxx(password for extension from asterisk)
host=(ip of HT503)

Prefix Dial Patters
76 XXX

Outbound route is set to use this trunk with same dial patterns

When I dial 76xxx it just rings and the Valcom is not acknowledging. If I just dial 76, I get “all circuits are busy now”

The obihai is a whole other story…

Anyone have experience integrating a gateway into an analog paging system?

Thanks for any help!

Why don’t you try setting the FXS port as an extension and not a trunk? Connect an analog phone to the FXS port to test whether it can receive a call, and if that test succeeds, then connect the paging device. As long as the paging device is set to auto-answer and is indeed expecting an FXS port on its input, then you will probably make it work that way.

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Done, plugging a handset into the gateway and setting as an extension in the PBX allows me to make and receive calls using the gateway. However, when I connect to the Valcom system, it causes the gateway to go off-hook.

So as soon as you connect the valcom device it goes immediately off hook? Or is that after you press some button on the valcom?

Immediately after plugging the Valcom into the gateway if shows off-hook. I am connecting to pin 1 & 26 on P7 of the Valcom connector, which is designated as a telephone system C.O. line port.

As far as I can tell from the pdf you attached, the valcom system is expecting a phone on 26&1 connectors, so you should be connecting the valcom to the FXO port, not the FXS, unless I’m missing something.

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