I manage customer sites that utilizes various types of hotline phones, including both third-party IP phones and analogue phones. These devices connect to the ATA or VG and are operational in refineries where their functionality is critical. We have never encountered issues with these phones.
We have, however, faced some challenges with the phone vendors. You have the option to choose any brand of third-party phones, whether analogue or IP. If you opt for analogue, you will need an ATA or VG for connectivity.
