• With the proliferation of Voice Over IP (VoIP) telephone technologies, Cisco phones have become a popular choice because of an extensive selection of models covering a wide range of needs. While they employ features specific to the Cisco VoIP servers, these phones can also be used with "open source" VoIP technologies. As the phones progress toward the 9900 series, more features become available. The models listed here range from basic cubicle phones to sophisticated phones that include video conferencing capabilities.
  
  

6900 Series

• This series of phones includes models with the same basic features, but the phones are distinguished by their line capacity, which ranges from two to 12. The 6900 series phone offers lighted hold and menu keys as well as a lighted call-waiting indicator. The series includes a speakerphone and interface for headsets. This entry-level phone offers a graphical display that can display basic images such as a corporate logo. The display also features scrollable menu selections to access additional features.
  
  

7900 Series

• The 7900 series includes a large number of models for specialized business needs. A brief survey of these models includes models 7910, 11 and 12. These phones are sets that offer minimal features. The phones in this model line are designed for common areas such as lobbies, classrooms or individual cubicles. The 7920 class includes all phones designed for mobile use. They are wireless models that connect to networks via the 802.11b and 802.11g protocols. The 7935, 36 and 37 are conference-station models that include external microphones and features suited to conduct corporate conference calls. The 7985 is a videophone that includes a high-quality camera and XGA computer LCD monitor.
  
  

8900 Series

• This series is described by Cisco as "an advanced professional media endpoint that delivers an enhanced user experience with an easy-to-use and eco-friendly ergonomic design." These phones feature high definition voice and video quality with a fast gigabyte network interface. In addition, they include VGA color computer-style displays and an external USB port. The 8900 series hosts a full feature set including programmable buttons, LEDs and the ability to handle as many as five call sessions simultaneously.
  
  

9900 Series

• This series makes up Cisco's highest-end phones. The series is described by the company as "an advanced collaborative media endpoint that provides voice, video, applications and accessories." The 9971, for example, features video conferencing as well as wired or wireless operation through 802.11g and Bluetooth. The LCD touch screen offers VGA resolution for ease of use and customization. These phone models are designed for high-end corporate executives and business administrators.