Video Teleconferencing (VTC)
Video Teleconferencing or VTC is the means by which two or more rooms containing Video Teleconferencing equipment, acting much like television studios, are linked electronically allowing the participants in one room to see and hear the participants in the other room.
This exchange is made possible by CODECs, which are coder/decoders. They take an analog input (the video and sound) and convert it to digital information for transmission. CODECs work just like a computer modem except in reverse (modems take digital information (from your computer) and change it to analog (sound) for transmission across regular telephone lines).
There are two types of videoconferences, point to point and multi-point. A point to point conference is a single Video Teleconference Facility (VTF) connected to another VTF by a transmission path. A multi-point conference is a connection of three or more facilities, allowing all participants see and hear the others. Multi-point conferences are a little more complex and require additional equipment. The additional equipment is called a Multipoint Control Unit or MCU. This MCU allows the signal from all of the conference participants to be combined.
Industry Standards For VTC
Industry Standards are developed to ensure that devices (including video) can "talk to each other". The International Telecommunications Union – Telecommunications Standardization Sector (ITU-T) is the worldwide body for setting industry standards for, among other things, Video Teleconferencing. In order to protect users and to ensure that all VTC equipment works together, the ITU-T developed the H.320 family of standards. The H.320 family covers many different aspects of Video Teleconferencing from VTC over regular phone lines to VTC over Local Area Networks (LAN). The baseline standard for VTC is H.320.