SIP - Voice alarming

Hello. I am fairly new to Ignition but am learning a lot as I develop my first substantial application.

I am looking to possibly include voice alarming for this project. Currently the old install (that I am replacing with Ignition) makes voice calls using a Dialogic board over a standard POTS telephone line. At this location there is Internet access but NO VOIP service installed.

I was hoping to find some sort of gateway that would allow me to use Ignition’s Voice module to trigger the dialout over the existing phone line and do this all within the physical location of this install.

I am aware that I could set up some sort of VOIP provider over the internet but I was hoping to avoid the monthly charges in this case.

Has anyone done this type of small scale voice dialout? And if so, what hardware did you use?

This knowledgebase article should be what you are looking for -
https://support.inductiveautomation.com/index.php?/Knowledgebase/Article/View/30/0/how-to-configure-the-grandstream-ht-503-for-use-with-ignition-alarming-voice

Thank you. This looks like it will be helpful.