SIP trunks can be used for a wide variety of call processing  solutions, some of which are very cost effective as in Free!   We have used  SIP tunks to interconnect ShoreTel systems over the Internet, complete with four digit dialing between systems!    Most recently,  we have been able to create a ShoreTel compatible audio conference server at a fraction of the cost normally associated with these servers.   The most costly part of  this conference solution  was the [...]