innovaphone gateway
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(often http or ftp) and the location of the resource in computer networks.
The name of the URI schema is therefore normally derived from the network
protocol used for this. Examples here are HTTP or FTP.
UTC
UTC (
U
niversal
T
ime
C
oordinated) is the current (coordinated) world time,
replacing in this function GMT time (
G
reenwich
M
ean
T
ime). It is a
combination of the international atomic time TAI (
T
empus
A
tomique
I
nternational) and the UT (
U
niversal
T
ime). The time zones are specified as
a positive or negative time difference from UTC (for example, UTC+2
corresponds to MEST). UTC combines the physical atomic time (TA) with the
astronomical time (UT), and is also called civil time.
µ-law
The µ-law method is a digitization method for analogue audio signals, which
is standardised in the G.711 recommendation of the ITU (
I
nternational
T
elecommunication
U
nion). Like the A-law method, the µ-law method uses a
logarithmic quantisation characteristic curve to achieve a better signal-to-
noise ratio. With this method, 8-bit values are likewise generated. However,
the quantisation characteristic curve for low levels is steeper. In addition, the
encoding is not designed to generate continuous sequences of 0s, but
continually changing bit states. In this way, a particular method for timing
recovery on the side of the receiver of the digital signal is simplified. The µ-
law method is used by the PCM technique in North America and Japan.
V
VLAN
VLANs (
V
irtual
L
ocal
A
rea
N
etwork) are a technological concept for
implementing logical workgroups within a network. This kind of network is
implemented using LAN switching or virtual routing on the data link layer or
on the network layer. Virtual networks are set up through a number of
switching hubs, which are connected together through a backbone.
VPN
The term VPN (
V
irtual
P
rivate
N
etwork) is used with different meanings.
Very generally, one refers to a VPN if customer-specific, logical subnetworks
are being created within a public switched network. They may be networks
for voice communication, or X.25, Frame Relay or ISDN networks. The usual
