3. The Terminology

Let's first repeat what the basic equipments used are:

• Codec - central unit that compresses outgoing and decompresses incoming video signal
• Digital camera - records pictures from your room
• Microphone - records the sound in your room
• Monitor with loudspeakers - see and hear the far end part(s)

Additionally, some additional peripherals are useful:

• Document camera
• Digital whiteboard and a video projector
• Laptop or stationary PC
• VHS/DVD-player

MCU - Multipoint Control Unit

The MCU - Multipoint Control Unit - is a unit that connects more than two parts in a videoconference. The unit is referred to as a bridge, as it connects 3 or more incoming and outgoing video signals. A MCU bridge operates on a mix of both ISDN and IP connections simultaneously.

Advanced video codecs (group systems) may have an internal MCU. These built-in MCUs have limited capacity with respect to bandwidth. If the demand for multi-part conferences is substantial, it may be profitable to buy a separate MCU bridge. But it should really be substantial, as MCUs are rather expensive. A better solution can be, at least at an early stage, to hire access to a MCU bridge from companies that have specialized on MCU services.

Monitor view in multipart conferences

The main operator decides which monitor view is to be shown.

	This monitor view is called "continuous presence", which implies that the screen is divided into several parts and everyone see each other.
	Here another monitor view is chosen. Only one of the participating groups is visible to all parties, either by the choice "voice activated camera view" or "assign floor".