Windstream Enterprise launched a new IP-based solution tailored to the need for critical safety voice applications. Digital Voice Lines (DVL) with Cellular Failover is designed to replace traditional Plain Old Telephone Services (POTs) as a more cost-effective and dependable alternative for customers. DVL over SD-WAN with cellular Failover provides the added benefits of superior network visibility, security, resiliency and performance. This VoIP service is available alongside SD WAN from Windstream for up to 100% uptime.
Source: https://www.helpnetsecurity.com/2021/07/30/windstream-enterprise-dvl/