The ESI eSIP 500x is the flagship real-time unified collaboration solution for on-site deployment for medium and large businesses.  It is a cost-effective business communication system, with a base configuration of 300 users and 60 concurrent calls.  It is expandable to 500 users and 120 concurrent calls, and 166 hours of voicemail.  This system grows with your business and supports up to 24 analog ports, up to 3 T1/PRI ports, and up to 6 Cellular channels and SIP trunks.  By integrating voice, video and data with mobility, your organization will benefit from increased productivity, particularly for users that work remotely and that are often on the move.  The ESI eSIP 500x enterprise business phone system has everything your organization needs to increase productivity, lower total operational costs, and to deliver an outstanding customer experience.