For companies wanting to make full use of the investment of an installed IP-PBX SIP trunking VoIP service provided by California Telecom to connect to the traditional Public Switched Telephone Network (PSTN) network may be the solution. Unlike in traditional telephony, where bundles of physical wires were once delivered from the service provider to a business, a SIP trunk allows a company to replace these traditional fixed PSTN lines with PSTN connectivity via a SIP trunking service.

SIP trunks can offer significant cost-savings for enterprises, eliminating the need for local PSTN gateways, costly ISDN BRIs (Basic Rate Interfaces) or PRIs (Primary Rate Interfaces). This type of VoIP service can drastically decrease company phone bills by as much as 40-70%.


There are some requirements and components necessary to successfully deploy SIP trunks.

The PBX
In most cases the PBX is an IP-based PBX, communicating with all endpoints over IP, but it may just as well be a traditional digital or analog PBX. The sole requirement is that an interface for SIP trunking connectivity is available.

Router/Firewall Edge Device
California Telecom will provide the router/firewall with complete support for SIP necessary for handling the traversal of the SIP traffic.

Service Provider
California Telecom is the Internet Telephone Service Provider (ITSP) that connects to the Public Switched Telephone Network (PSTN).