The MyPBX U100 is a 1U rack mount IP PBX that supports up to 100 users and 25 simultaneous calls. It has integrated ISDN, PSTN, GSM and VoIP connectivity. It provides enterprise-grade features for small and medium businesses at no additional cost, including automated attendant, call forwarding, call parking and call routing. The system can also integrate with firewalls and enable centralized VOIP across multiple sites with extension dialing between locations and mobile app integration for remote users.