Codan Radio P25 Training Guide - Manual (Page 115)

P25 RADIO SYSTEMS | TRAINING GUIDE
Chapter 9: P25 Glossary of Terms Page 107
PBX
Abbreviation for “Private Branch
Exchange.” A privately owned switch,
generally of relatively small size,
connected via output trunks to the public
switched telephone network.
PCM
Abbreviation for “Pulse Coded
Modulation.” That form of modulation
in which the modulating signal is
sequentially sampled, quantized,
and coded into a binary form for
transmission over a digital link.
PDT
Abbreviation for “Portable Data
Terminal”
›/4 DQPSK
Abbreviation for “Differential Quadrature
Phase Shift Keying” modulation
technique. ›/4 indicates 90° phase
angles.
›/4 QPSK
Abbreviation for “Quadrature Phase
Shift Keying” modulation technique. PSK
using four phase states. ›/4 indicates
90° phase angles.
PN Sequence
A pseudo random BIT sequence used in
vocoding.
Polling
A network control system in which a
designated control station invites its
tributary stations to transmit in any
sequence specifi ed by the control
station.
POTS
Abbreviation for “Plain Old Telephone
Service.”
PPP
Abbreviation for “Point-to-Point
Protocol.”
Processing Delay
The time in ms required for the
coding and decoding of voice or data
information.
Protocol
A set of unique rules specifying a
sequence of actions necessary to
perform a communications function.
PSDN
Abbreviation for “Public Switched Data
Network.”
PSK
Abbreviation for “Phase Shift Keying.”
A method of modulation used for digital
transmission wherein the phase of the
carrier is discretely varied in relation to
a reference phase, or the phase of the
previous signal element, in accordance
with the data to be transmitted.
PSTN
Abbreviation for “Public Switched
Telephone Network.”
PTT
Abbreviation for “Push-to-Talk”, the
switch on a subscriber unit which, when
pressed, causes the subscriber unit to
transmit.
Quadrature Modulation
Modulation of two carrier components
90° apart in phase by separate
modulating functions.
QAM
Abbreviation for “Quadrature Amplitude
Modulation.” Quadrature modulation
in which some form of amplitude
modulation is used for both inputs.
QPSK
Abbreviation for “Quadrature Phase
Shift Keying” modulation technique. PSK
using four phase states.
Reed-Solomon (RS)
An error correction coding scheme for
binary data fi elds.
Reference Vocoder
The particular implementation of the
APCO Project Vocoder available from
Digital Voice Systems Incorporated as
Model VC-20-PRJ25. This is the agreed
upon reference implementation of the
APCO Project 25 Vocoder.