Orbtalk have a range of SIP trunk products that work with the Epygi Quadro
The Epygi Quadro Family offers reliable, versatile, and cost-effective iPBXs that fulfill the communication needs of small businesses, branch offices and home offices.
The Quadro IPBX supports both regular PSTN lines and low cost VoIP Service providers. Just connect a Quadro to your broadband Internet service and it automatically configures itself and in minutes you are able to make voice over IP calls for free.