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MERLIN LEGENDCommunications System Release 6.1
System Planning
555-661-112
Issue 1
August 1998
Glossary
Page GL-28
V
W
unrestricted data
channel
Unrestricted data channels (also called clear data
channels) allow the transmission of occurrences of more
than seven contiguous zero bits. If an unrestricted data
channel is requested and only restricted channels are
available, the call will be rejected. See also restricted data
channel.
UPS (uninterruptible power supply) Device that connects to the
system to provide 117 VAC to the equipment when the
commercial power source fails.
VAC (alternating-current voltage)
VDC (direct-current voltage)
VMI (voice messaging interface) An enhanced
tip/ring
port.
videoconferencing
system
System application that allows face-to-face meetings, with
voice and video, to occur between individuals or groups.
This application requires high-speed data transmission
facilities. See also
desktop videoconferencing
and
group
videoconferencing.
virtual private
network
See
VPN
.
VPN (virtual private network) A type of
private network
that uses
the switching capabilities of the
PSTN
, rather than
tandem
switching
, to direct calls between connected
communications systems. A VPN may constitute a part of a
private network.
voice-band
channel
A transmission channel, generally in the 300–3400-Hz
frequency band.
voice mail Application that allows users to send messages to other
system extensions, forward messages received with
comments, and reply to messages.
voice messaging
interface
See
VMI
.
WATS (Wide Area Telecommunications Service) Service that
allows calls to certain areas for a flat-rate charge based on
expected usage.
wink-start tie trunk
Tie trunk
on which the originating end transmits an off-hook
signal and waits for the remote end to send back a signal (a
wink) that it is ready for transmission.