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Use an analogue intercom with a VOIP PBX system, like 3CX

I have recently deployed a 3CX system to a customer’s home, replacing an old NEC phone system that was installed some time in the 1990s. As much as I loved the 90s, phones have come a long way since then.

One component that I wasn’t able to completely digitise was the intercom and gate release for the front gate. We traced out the cables going down the long driveway, and we didn’t have a straight-through connection on a single piece of Cat 5 in order to run Ethernet.

The existing intercom at the front gate is a simple analogue system with just a single pair of wires used to carry voice to/from the panel, and a separate pair of wires used to open the gate – when this second pair of wires are shorted, the gate will open.

In searching around, I have come across an excellent piece of hardware that has allowed me to retain the analogue intercom, and gate opener, but still let me connect it to a 3CX PBX.

The device in question is the Natcomm DS-SIP which is like an ATA for analogue intercoms. Much to my delight, not only is the company located in Australia, but the owner, Ron, has provided me with absolutely first-class support in getting this unit up and running.

The DS-SIP module uses an embedded Patton SN200 ATA/VOIP Gateway, along with some of Ron’s magic that allows it to trigger relays to open one or two doors or gates.

Current versions of 3CX have support for the SN200 ATA straight out of the box, however it wasn’t quite as straightforward as this, as when this module is used in the DS-SIP there needs to be additional configuration, for example, to hot-dial a particular number as soon as the intercom goes off-hook.

The DS-SIP has a built-in wizard that allows all of these particular parameters to be configured, however this configuration wasn’t successfully authenticating against the 3CX PBX. The configuration wizard within 3CX generated a config file that had the device successfully authenticate, however with this config, there wasn’t any way to specify a the hot-dial extension number.

Fortunately, both Ron at Natcomm and the technical support team at Patton were very responsive, and I was able to give them the two different config files (one from the Natcomm wizard and one from 3CX) and they merged the relevant parts into a single config file that I was able to upload to the device and have it all work.

If you’re looking for a reliable, and highly configurable device to run an analogue intercom and door or gate release from a VOIP PBX, I definitely recommend checking out the DS-SIP.

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