Please be aware that electrical power is required for non-line-powered voice services (including Digital Home Phone) to work. If there is a power outage, the services will not process calls, including those to Emergency 911.
A BBU will improve the ability of these voice services to function during a power outage event. With active good batteries, the BBU will provide temporary backup power for the network equipment and devices in your home that are necessary to provide basic voice services as well as access to dial Emergency 911. (The BBU may not guarantee functionality in the event of a power outage depending on the nature of the outage or if the service network is out of operation.) As a separate service, you may purchase any necessary BBUs, including the housing, from CenturyLink, or you may purchase a backup battery solution from another supplier and install it yourself.
When you talk to a CenturyLink Service Representative, you can discuss the type of service you have and what battery or batteries you may need.