Instead of connecting phones to an on-premise PBX, RingCentral phones plug into your router and connect across the Internet to RingCentral data centres. Smart apps can then be installed on your devices to transform them into powerful extensions of your business phone system. This process is especially effective for business that operate both in and out of the office and the typical cost saving is over 50%. We have over 300,000 clients. http://www.ringcentral.co.uk/