A SIP PRI gateway is a device that allows for the conversion of traditional T1/E1 PRI (Primary Rate Interface) lines to SIP (Session Initiation Protocol) trunks. This enables businesses to connect their existing phone systems to a SIP-based network, allowing for more flexibility, scalability, and cost savings. The SIP PRI gateway acts as an interface between the traditional phone system and the SIP network, facilitating the routing of voice calls over IP networks.