Page 57 - Intelligent Communication Systems

CHAPTER 5 / AVARIETY OF TELECOMMUNICATION SYSTEMS 4 I

FIGURE 5.4 Audio conferencing system.

FIGURE 5.5 Audiographic conferencing system.

Then during the class, students can retrieve information from their terminals in
real time. In this system, the students who attend the class at remote places cannot
be seen, so their pictures are posted on a board. A diagram of the setup is shown
on Figure 5.5.

5.4.3 Video Conferencing System
In the video conferencing system, two channels are used to transmit both audio
and video signals. It takes a lot of bandwidth to transmit video signals. Though
expensive, this system has been widely used in distance education. Students not
only see each other but also hear one another's voices and can see the text or
graphics transmitted from the remote site. To reduce the cost, video compression
technology has been developed and installed in the system. This includes
MPEG1 andMPEG2 video compression technologies. MPEG1 provides 1.5 Mbits