FreeSWITCH is an open-source, cross-platform telephony engine designed to route and interconnect popular communication protocols using audio, video, text, and other forms of media. Unlike Asterisk (another popular PBX), FreeSWITCH uses a core architecture that is highly modular, event-driven, and capable of handling thousands of concurrent calls per second without choking.
: Instruction on using Regular Expressions (PCRE) to route calls. Configuration files are typically found in /usr/local/freeswitch/conf/ . External Integration (ESL & mod_xml_curl) : freeswitch 18 pdf