The Cisco SPA 504G is a full-featured 4-line small business phone that provide a rich user experience with Cisco HD Voice to for unsurpassed voice clarity, a monochrome backlit display for ease of use and aesthetics , XML that deliver enhance productivity, security, and customer service applications, encryption for enhanced security, enhanced full duplex speaker phone for clear conversations across the desk, and intuitive end user menu options, for use with SBCS and Cisco SPA 9000, as well as being interoperable with major 3rd party SIP application servers for use in Open Source or Hosted IP Telephony Solutions.