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Another option with Multipoint working is “Chairman Control” where all sites receive pictures from the Chair site alone. The Chair site will see images from the remote site currently speaking. All sites receive all sound. 

Conferencing between two sites is termed “Point to Point” and is the most frequently used method. It only requires equipment at each site and the network of choice. If more than two sites require a simultaneous conference, this is termed “Multipoint” conferencing, and an additional specialised piece of equipment is required, called a “Multipoint Control Unit” or MCU. Some videoconferencing CODECs can support limited multipoint working (e.g. up to 4 sites). Generally, MCU’s are very expensive and are rented from service providers just for the duration of a conference.

As has been previously mentioned, a CODEC is necessary to enable the sound and vision signals to be converted and then transmitted from the local site. Another CODEC is also required at the remote site to convert the digital signals back into sound and vision signals for the audience. The method of transmission for IP and ISDN are different and so require different CODECs.

All schools now have access to the World Wide Web via the Internet. This technology uses a common method of transmitting and receiving data called IP or Internet Protocol standard to ensure information passes flawlessly between networks. The success of the WWW could not have been achieved without this single ubiquitous standard. A disadvantage of IP transmission is that because all data traffic e.g. e-mails, WWW downloads or videoconferencing has to share the same pipes, they all have to compete for the available space or bandwidth.