VTScada should work with any standard voice modem. Though we cannot guarantee the compatibility of third-party modems across all Windows operating systems our engineers have provided the following comments on modems that they have used or have been used by our customers.
Their comments can be found on our VTScada Support Forum:
https://forum.trihedral.com/index.php?u=/topic/93/how-do-i-choose-a-voice-modem-for-my-vtscada-system