I am currently using an analog modem for VTS dial out alarming, and am looking to shift to VOIP.

I know that VTS supports Twilio, but are there any other VOIP providers that VTS supports?

At this time, we would suggest the Grandstream HT813 for VoIP, if you are planning to purchase new hardware. To get VoIP working with existing or new hardware, please check out: https://www.vtscada.com/help/Content/D_AlarmSystem/Dev_VOIP.htm

I'm telling you about my most recent encounter with Knot Networks, a superb US distributor of Voip Telephony. Try them if you're searching for reliable and feature rich Voip Telephony.
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