ETV - Educational Television

Videoconferencing

Technical Information

A basic videoconferencing system consists of a videoconference codec, a video monitor, camera, one or more microphones and an audio speaker. We can include additional peripherals to the system to enhance collaboration, such as a document camera, computer, videotape or disc player and recorder and external video and audio sources. You connect with the distant site by dialing into their videoconferencing system similar to dialing a telephone. Videoconference connections use ISDN (Integrated Services Digital Network), LAN (Local Area Network) or a dedicated circuit, such as a T-1. At Palomar College, you can connect to a distant site via ISDN or T-1. ISDN is an economical solution for high-quality videoconferencing. ISDN works over regular copper telephone lines, transmits at a minimum of 128 Kbps per line and provides dedicated bandwidth for smooth audio and video (15-30 frames per second). The T-1 is part of a dedicated data and video distribution system called the 4CNet administered by the Cal State University Chancellor's Office in cooperation with the California Community Colleges Chancellor's Office. The established transmission rate for videoconferences is 384 Kbps.

There are two types of videoconference meetings - point-to-point, a conference between two sites, and multipoint, a conference between three or more sites. To participate in a point-to-point videoconference, one site dials the other site's ISDN videophone number. In a multipoint conference, each site dials an ISDN videophone number to a video bridge at one site, or connects via a video bridge service company for a fee. Newer videoconferencing systems have built-in video bridges that allow you to conference with multiple distant sites just as you would in a point-to-point conference call. You can even add other sites at anytime during the conference. These newer videoconferencing systems eliminate the need to schedule and pay fees for time on a video bridge. ISDN videoconferencing systems adhere to H.320 standards, which means that any standards-compliant system can connect to any other ISDN H.320 standards-compliant videoconferencing system in the world.

During a multipoint conference, you are able to see and hear one or more sites. There are two types of multipoint videoconference calls: voice-activated and continuous presence. A voice-activated conference call will allow you to conference with multiple distant sites. The video switches between sites only when someone speaks and activates the audio. Everyone only sees one site on the video monitor in a voice-activated conference call. During a voice-activated conference call, if no one speaks at a site, you will see only the person that last spoke. In a continuous presence conference, each site views in quadrants up to four sites simultaneously on the video monitor. If more than four sites are connected, one quadrant toggles between the remaining sites when someone activates the audio. An advantage of a continuous presence conference call is that multiple sites are always seen on the video monitor. Many of the new videoconferencing units support continuous presence.

A T-1 videoconferencing call can be voice activated or continuous presence. A T-1 line is a dedicated service between two sites. Palomar College's T-1 connection links between Palomar College (located at ETV) and the 4CNet Network Operations Center in Los Alamitos, California. The 4CNet Center operates a video switching and bridging service for the California State Universities and California community colleges. ETV's videoconferencing coordinator will use the 4CNet scheduler to reserve your videoconference with any other community college, California State University or system administrative office. Click here to view the list of 4CNet videoconference sites.

We welcome your questions and comments, please call 760-744-1150 ext. 2431, or send and e-mail to videoconference@palomar.edu