The biggest difference among video conferencing systems is how the signals are transmitted. The particular method can have a big impact on the connection options, as well as the quality, speed and cost of the transmission. Most systems today are based on standards, so that systems using different equipment but the same standard can connect without special equipment. Two of the most common standards are H.320 (ISDN) and H.323 (IP). Other standards also exist, such as T.120, which enables data sharing, and H.243, which enables multipoint conferencing, or communication among more than two locations.
ISDN- (integrated services digital network-) based systems use existing phone lines to transmit data, whereas IP- (Internet protocol-) based systems use Internet networks. Many schools seem to like ISDN because it establishes a dedicated link unaffected by other users. This makes the quality of an ISDN connection predictable. The drawbacks to ISDN are that it isn't always available in rural areas and that it racks up per-minute long-distance charges. To connect with other users, people using ISDN-based systems simply dial the number of who they want to connect with, like a regular phone call.
IP-based videoconferencing, on the other hand, costs less, especially as network connections become more prevalent. Since it uses the Internet infrastructure, and many schools already have existing networks, using an IP network doesn't require setting up any special connections. However, depending on the network's capacity, signal transmissions can be slow and unreliable. If many other people are using the network, the quality of the video conference may be negatively affected. With the introduction of broadband and other improved Internet technologies, though, IP-based video conferencing is gaining in popularity.
Aside from the different standards used to connect, the physical arrangement of classroom video conferencing equipment also varies. Some schools have rooms dedicated to the technology, while others have portable systems or even desktop units.
- Integrated systems are the most advanced setups and are generally used for more formal communication. Prices start at around $10,000 and can go as high as $100,000 [source: IVCi]. Here, the video conferencing equipment is incorporated into the classroom's design and usually consists of several monitors for displaying video, multiple microphones to capture sound and top-of-the-line codecs to deliver optimal quality. You typically see these systems in classrooms where one person is addressing many people, such as in distance learning.
- Portable units are less expensive than the integrated systems at about $5,000 to $10,000 [source: IVCi]. These portable setups typically consist of the monitor, microphone, camera and other equipment loaded onto a rolling cart that can be transported to whichever classroom needs it. Although these small units are ideal for sharing, they limit the ability to add additional equipment, and since they must be hooked up every time they are moved, a basic knowledge of the technology is helpful.
- Desktop setups are the cheapest method of video conferencing at about $300 if you already have the computer [source: IVCi]. At their simplest, this setup includes a PC, a small camera mounted on top, a microphone and software to perform the job of the codec. Some newer computers come with this software already installed. This design isn't conducive to classroom use, but is more appropriate for one-on-one informal communication.
Teaching methods have come a long way since the days of the blackboard and one-room schoolhouse. If you want to learn even more about video conferencing lessons for schools, follow the links on the subsequent page.