Stanford Diehl
Target Technologies (Wilmington, NC) has come up with a relatively inexpensive way of putting videoconferencing on existing LANs without bogging down the network. The system, called C-Phone, uses a PBX model to deliver desktop videoconferencing to both LAN stations and remote locations. With C-Phone installed on an Ethernet network, you can make live video phone calls from your desktop to any other C-Phone installation on the LAN.
A C-Phone gateway connects the video phone to the outside world. The Windows software supports a telephone-style interface that any business office can easily grasp. You simply start up a C-Phone session, check your image to make sure you've wiped the doughnut crumbs off your chin, and select the person you want to call up from a list. The part
y on the other end receives a ring, decides to accept the call, and--after wiping his or her own chin--picks up the line.
C-Phone is a hardware and software solution selling for $1995 per PC. An integrated camera/microphone/speaker unit sits on top of the PC's monitor. C-Phone requires a 386-based PC or better, running Microsoft Windows over Novel Netware, Artisoft Lantastic, a NetBIOS-compatible network, or Windows for Workgroups. The video system supports 64 lines (32 simultaneous two-way calls) on each workgroup. Bridging hardware for calling across multiple LANs and WANs is not yet available.
C-Phone operates out-of-band, consuming bandwidth not occupied by Ethernet traffic, so the video network does not degrade LAN performance. Your LAN cabling must be a shielded type to keep external high-frequency signals from interfering with the C-Phone traffic. If not, you must upgrade your network cabling or install dedicated cabling for the video network.
The optional C-Gate gateway connects t
he video phone system to the outside world via ISDN (BRI, or Basic Rate Interface), Switched 56, or T1 lines. Again, the PBX metaphor applies. Callers on the in-house video phone system share a set of outgoing lines. A number of different compression engines sit on a server, offering callers H.261 compression (for connection with other H.320-compatible conferencing systems, including room-based systems), Indeo compression, or other proprietary codecs. The caller dials out, selects a compression engine, and receives the first available ``trunk.''
The software supports 720- by 484- pixel picture resolution at 30 frames per second over the LAN, or CIF (Common Intermediate Format) resolution (352 by 288 pixels) at 15 fps over BRI. You can view multiple people taking part in the conference on a divided screen (a ``Hollywood Squares'' scenario), or broadcast one caller to many recipients. The software also supports standard telephone features such as caller ID, call waiting, call forwarding, call hold, and s
tored messages that can be played back, forwarded, replied to, or archived. C-Phone does not come bundled with any whiteboard or application-sharing software, although a whiteboard program running on a standard phone line could operate in conjunction with C-Phone. And the software developer's kit will allow developers to support C-Phone in other software packages.
Stanford Diehl is director of the BYTE Lab. You can reach him on the Internet at
sdiehl@bix.com
.
The C-Phone Solution: Out of Band
