A VOIP PRI service is a Primary Rate Interface phone service using Voice over IP to transport calls over public or private IP networks. PRI VOIP service is used by businesses to provide local and long distance voice service as well as other applications. VOIP PRI service provides increased efficiency through a PRI IP PBX phone system by utilizing IP network access for VOIP calls through a CPE with a PRI T1 handoff. This eliminates the need for a traditional ISDN PRI T1 service or regular phone lines. An IP PRI T1 also offers the same benefits and features as a traditional ISDN PRI T1, including faster call connection, Caller ID, and Direct Inward Dialing (DID) through the D channel signaling on the VOIP PRI line. PRI VOIP service is very flexible and can scale quickly with additional bandwidth added. VOIP PRI lines are also known as an IP PRI, Flex PRI, Dynamic PRI, T1 VOIP, or SIP PRI.