Application Sharing
Shared viewing, manipulation and exchange of documents and files during a videoconference. The application sharing standard is the ITU recommendation T.120 which is, among others, supported by MS NetMeeting software.

B
Basic Access
ISDN connection via S0 interface, consisting of wo 64 kbps data channels (B channels) and a 16 kbps data channel (D channel).

B-Channel
Channel for ISDN data transfer a 64 kbps.

Bridge
Link between two or more networks. A bridge can only link networks of identical topology (e.g. Ethernet) that use the same protocols.

BRI
Basic Rate Interface. International term for the ISDN basic access.

Top

C
Channel Bundling
Merging of several B channels. These are treated as a virtual channel, resulting in increased data transfer speed.

Cart
Monitor car on wheels.

CAPI
Common ISDN-API. Standardised interface for ISDN cards.

Chairman
Person heading a multipoint conference. The chairman decides which location is shown as a full-screen image to participants.

CODEC
Coding/decoding and compression/decompression of videoconferencing signals according to a certain protocol. These protocols were standardised by ITU. The transformations are handled by a special CODEC card which usually also houses the communication interfaces (ISDN/LAN).

Continuous Presence (Quarter Split)
IA multipoint conference type supporting video and audio communication between four locations. Each participant's screen is divided into four zones. Each zone displays one of the remote locations.

Cryptor (Encryptor)
Encryption and decryption systems are used to ensure secure data exchange. These devices must be installed a both the sending and receiving location.

Top

D
Data Compression
Method for increasing the effective data transfer rate. Mathematical algorithms are used to reduce the size of electronic files.

D-Channel
Channel for transfer of ISDN service information. The D channel is used to transmit signals required for establishing and terminating the connection. 1TR6 and DSS1 are different, incompatible D channel protocols.

Downspeeding
Safety feature in charge of maintaining a connection in case of a partial B channel failure.

DSP
Digital signal processor or single-chip microprocessor which autonomously controls processes and performs calculations in electronic systems.

DuoVideo
Image transfer mode for the simultaneous exchange of two live video images between two videoconferencing systems.

Top

E
Echo Cancellation
Technology for suppressing (filtering) echo feedback during voice transmission. This significantly improves the transmitted voice quality.

Ethernet
IT network with a bus architecture. At present the most widespread technology for local networks.

F
Fixed Line
Permanently active connection between two parties within a network. No other participant can use this connection.

Firewall
A firewall protects data networks from external threats. All data traffic between the network and the outside world must pass the firewall. Only data deemed safe according to the security specification may pass.

Frames
Images displayed on monitors (1 frame = 1 complete image)

Full Duplex
Capability for simultaneously sending/receiving data at maximum speed.

Top

G
Gateway (for videoconferences)
A gateway enables H.323-compliant systems to communicate with H.32x-type remote systems. The gateway can, for example, link the H.323 system to a system based on H.320 (ISDN), H.321 (ATM), H.322 (ISO Ethernet) or H.324 (PSTN). At present, an H.323-to-H.323 connection (LAN/LAN) is the most common form of VC gateway connection.

I
ICM
Intelligent Call Management - function that dynamically controls and splits up the transfer bandwidth between video, audio and data information.

IMUX
Inverse Multiplexer - handles multi-channel transmission management of ISDN video/data communication.

IP
Internet Protocol.

ISDN
Integrated Services Digital Network. Digital network that offers all services (voice, text, images, data) via a common connection.

ITU
International Telecommunications Union - United Nations (UN) committee with 113 participating countries. It devises data transmission standards for telecommunications and global networks.

Top

L
LAN
Local Area Network - system of interconnected computers within a defined area.

M
MCU
Multipoin Control Unit - technology for enabling and controlling conferences with more than two participants.

Multiplexer
see IMUX.

N
NetMeeting
Microsof NetMeeting 3.0 allows users to share audio, video, files and applications in real time and across different connections. Available functions differ depending on the type of connection. Audio and video support requires a TCP/IP connection via a local network (LAN) or the Internet.

NT
Network Terminator.

NTSC
American video standard (60 Hz network frequency).

Top

P
PAL
European video standard (50 Hz network frequency).

PBX
Private Branch Exchange - private TC branch exchange.

PCI
Bus format for PC plug-in cards.

Plug & Play
Term used to point out that installation of a device or software is very easy and user-friendly.

POTS
Plain Old Telephone Service. Analogue telephone line employing e.g. twisted-pair cables for transmission of modulated voice signals. See also PSTN.

PSTN
Public Switched Telephone Network - the (analogue) public-fixed telephone network.

Q
Quality of Service
QoS guarantees network resources required by an application by means of providing a guaranteed bandwidth. Key requirement for videoconferences and Voice over IP (VoIP).

R
Remote Management
Controlling a device at a remote location.

Router
Linking multiple networks.Network topologies need not to be identical (i.e. Token Ring and Ethernet).

Top

S
S0-Schnittstelle
ISDN connection, consisting of two B channels and a D channel.

S2M-Schnittstelle
ISDN connection, consisting of 30 B channels and a D channel.

SoftMux
Software-based IMUX (see IMUX). Copyright by Tandberg.

Streaming Video
Providing and sending video, audio and text information to one or more participants on the intranet/internet. Thus streaming video is a one-way communication form. Feedback is only possible per online chat .

W
W.A.V.E. Camera
Wide Angle View Camera - camera covering an especially large area (viewing angle + swivel/tilt radius).

WAN
Wide Area Network - network linking PCs or LANs via public or private telecommunications networks.