Viking IP products are riding the wave of customer's efforts to replace analog (POTS) lines with a newer type of service that utilizes a network connection instead of a twisted pair of wires. This technology is called VOIP (stands for: Voice Over IP)
In the past, the phone Central Office provided talk battery, dial tone, and ringing signals to phones and PBX'es, FAX machines, modems, and etc.
In this new world, VOIP devices that need to originate or receive calls to/from the outside world (PSTN - or similar) require:
A network connection - RJ-45 connection to a network switch/router.
Power - the connection listed above MUST also provide voltage for the intercom/device to function.
( this is called "PoE" or Power-Over_Ethernet) - either via a PoE switch or a PoE injector.
VOIP Provider - this can be an on-premise device or a cloud-based service that is based upon a subscription model. Each device requires configuration within the provider's administration portal.
The results of that are a SIP provider URL, Outgoing Proxy URL, Username, Password (at the very minimum). These settings are keyed into the Viking device on the "IP Settings" page.
If all is configured properly, the Viking device will register with the VOIP provider and be able to originate and/or receive phone calls.