Polycom VIEWSTATION Training Manual page 36

End-User Training Guide: ViewStation
Compression
– Reduction of the amount of information to accommodate
cost-effective digital transmission to another codec. For example, sub-T1
video codecs compress analog signals (roughly equivalent to 90,000 kbps) to
digital rates varying from 56 to 1,544 kbps.
Compression Ratio
– A compression ratio, usually expressed as 5:1, refers
to the size of the original data versus the size after compression. If data has
been reduced to one-fifth the original size, the compression ratio is 5:1.
Dedicated Line
– A permanently assigned path connecting geographically
dispersed sites on a long distance network. Synonym: private line: leased
line.
Delay
– Refers to the slight delay that sometimes occurs when transferring
video, data and audio signals.
DES
– Digital Encryption Standard, an encryption method defined by the
National Bureau of Standards.
For more
Digital
– Information contained in the form of 0s and 1s for transmission on
information
digital media, including fiber, microwave, and satellite. Digital information
call
may include video, audio, graphics, and data.
408-402-9000
Digital Service Unit (DSU)
– A type of customer premises equipment that
terminates a single DSO or fractional T1.
DSO
– Digital Signal level zero. One 56 kbps (or 64 kbps) line or circuit.
DS1
– Digital Signal level one. One 1.544 mbps digital signal comprised of
24 lines or channels, each with 64 kbps capacity (see T1).
Digital Switch
– A means of supporting multiway conferencing using the
signals in their digital format without converting them to analog. Digital
switches permit multiple users with similar codecs to conference generally
with voice-activated switching.
Dual 56
– Combination of two 56 kbps lines for a 112 kbps video
transmission capacity. Dual 56 typically allows direct dialing of a
videoconference call.
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VSGi - Polycom ViewStation End-user Training Guide