Are you interested in VoIP but already invested in an on-premise PBX? Then a SIP Trunk (Session Initiation Protocol) is the best way to change your traditional phone systems to a VoIP phone system. The SIP Trunk enables your premise-based PBX to send and receive phone calls over the internet as opposed to an analog phone line. Your on-premise PBX will still be in use to manage your phones, but the SIP Trunk will connect the PBX to the internet providing more cost-effective service to your phones. If eventually choose to switch your on-premise PBX to a cloud-based PBX this is still easily done by removing the SIP Trunk.