A PBX uses trunking to send and receive phone calls. A SIP trunk provides this service by using IP (Internet) rather than the legacy switched telephone network. SIP trunks are typically faster, easier to use and less expensive. A SIP trunk can provide dial tone for both IP and traditional analog PBX. As with analog trunking, one SIP trunk allows for one phone call.

SIP trunks have superior call quality, are easier to install, and easily integrate with IP PBX to allow the advanced functionality of VoIP systems that are not available through analog systems. SIP trunks are usually much less expensive than SIP trunking, and SIP trunks can operate over your existing Internet connection.

PRI are often bunched into groups of 23 trunks via a separate dedicated T1. SIP trunks can be bought as they are needed and may be delivered as priority traffic over a normal or private Internet connection. And typically, SIP trunks have significantly less expensive per minute long distance costs, if any.

SIP trunking is for businesses that prefer to operate their own phone system hardware, or who are committed to a legacy system but wish to reduce existing costs without upgrading. Hosted PBX is for new or established businesses that want to save money in the long term while removing the burden of staffing maintenance of a legacy PBX.

Any PBX can use SIP trunking. If the PBX is not already SIP capable, it likely has an optional module. For pure analog PBX systems, a simple Analog Telephone Adapter can be installed which converts the digital SIP signal into analog dial tones that connect to your PBX just like a regular phone line.

This depends on various factors including the size of the Internet connection, the number of trunks used, the preferred codec and the ability to prioritize traffic at the customer premise. In general, a SIP trunk uses very little bandwidth, and modern HD codecs use amazing compression to provide CD quality phone calls with a tiny amount of data. XMission engineers will help every customer determine what will be the best solution for their office.