The Viewpoint VBX� Small Office server is designed to meet the needs of the modest-size organization with a requirement for leading-edge video on a limited budget. This server can manage up to 16 clients. It consists a tower-configuration PC running the Windows NT 4.0 operating system. The PC is based on a passive backplane with ISA and PCI card slots, and a Pentium CPU on a card. Codecs for wide-area interface may be mounted within the server.
Each small office server can handle up to 32 one-way or 16 two-way users. Two Viewpoint VBX� control cards are included in the configuration. VBX cards are full-length ISA cards that plug into standard ISA slots in the passive backplane. External VBX connections from each card are located at the backplate of each card. DIP switches on each card set the card address to allow the software to control the card.
The Viewpoint VBX� Server software running on the PC performs the following functions:
- Communicates with clients and other servers
- Maintains a database of installed hardware and connected users
- Controls the flow of video and audio through the switch
- Logs the system usage for management and billing purposes
Software for the management of the Codecs runs as a separate process, communicating directly with the server software. Control of Viewpoint VBX�-based communications is performed using the existing LAN infrastructure. The WorkFone VBX client software, running on an individual workstation, communicates with the server software, running on the VBX Server using the TCP/IP protocol. Messages passed from client to server include Dial User, Get Directory Listing, and Hang Up. Messages typically use only a few bytes (a directory listing may use a few hundred bytes), so there is virtually no impact on other LAN traffic.
Audio and video data travels off the LAN. Because video and audio are passed over dedicated UTP wiring, there is no effect on network data traffic. The Viewpoint VBX� makes use of spare Unshielded Twisted Pair (UTP) wiring for distribution of video and audio. Each twisted wire pair can carry both video and audio in one direction up to 3,500 feet. Most installed UTP cabling includes four twisted pairs (a total of eight wires). Of these, only two pairs are used by 10BaseT Ethernet networks, leaving two unused pairs. Using these two spare pairs, the VBX Server can implement bi-directional video and audio communication. In addition to these spare wires, many installations run multiple four-pair UTP cables to each destination. Even if no UTP cabling is available in your facility, UTP cabling is easier and much less expensive to install than coaxial (coax) cable. Like 10BaseT Ethernet networks, Viewpoint VBX UTP connections use a hub-and-spoke topology where each user is wired directly to the VBX Server.
