Snom Technology is a company which manufactures Voice over Internet Protocol (VoIP) telephones, based on the IETF standard Session Initiation Protocol (SIP). Snom delivers the best audio performance in the world. All of snom’s software exists in the firmware of its phones, and VoIP telephones support all common standards. Also it compatible with SIP-based telephone systems and system components, including IP-PBX systems offered by companies and a very secure system too.
Asterisk is an open source framework for building communications applications. It powers IP PBX systems, VoIP gateways, conference servers and other custom solutions. Also it can become the basis for a complete business phone system, or used to enhance or extend an existing system, or to bridge a gap between systems. Asterisk is flexible, lets you define the solution that truly fits your requirements and It is stable, reliable and in production on thousands of systems worldwide. It is free to use.