Page 130 innovaphone gateway
network in public communication technology.
P
PL
PL (Packet Loss) occurs during packet-based data transfer in networks.
Packet loss can occur in various layers of the OSI model.
PCM
PCM (Pulse Code Modulation) is an ITU standard for the digitization of
voice, which is described in G.711. With this type of modulation, analogue
signals are converted to discrete-time and discrete-value binary signals
through quantisation.
In voice transmission, the PCM technique is used to convert an analogue
voice signal to a digital signal based on Nyquist’s sampling theorem. For this,
the analogue signal is sampled 8,000 times per second and is converted to
an 8-bit number, so that a sample value arises every 125 µs. The resulting
transfer speed is 64 kbit/s, the transferable voice frequency 4 kHz.
For the dynamisation of voice, the ITU within G.711 has defined two
methods for the dynamic compression: the µ-law method and the A-law
method.
PING
The ping program (Packet Internet Grouper) can be used to check whether
a particular host in an IP network is accessible and what its response time is.
POE
PoE (Power over Ethernet) describes a technology, with which network-
enabled devices can be supplied with power over the 8-wire Ethernet cable.
POSIX
POSIX (Portable Operating System Interface for UniX) is a standardised
application-level interface jointly developed by the IEEE (Institute of
Electrical and Electronics Engineers) and the Open Group for Unix. It
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