7E Communications
   

Glossary Terms Beginning P

0-9 : A : B : C : D : E : F : G : H : I : J : K : L : M

N : O : P : Q : R : S : T : U : V : W : X : Y : Z

Packet-switching
Data transmission method that divides messages into standard-sized packets for greater efficiency of routing and transport through a network.
Panning-up
Process of accurately aligning satellite uplink antenna to the satellite.
Parabolic antenna
Antenna with a reflector described mathematically as a parabola; essentially an electromagnetic wave lens which focuses the radio frequency energy into a narrow beam.
Payload
Load carrying capacity; on a rocket launch vehicle, the satellite is the payload.
PCM
Pulse code modulation.
Perceptual coding
A coding technique which takes advantage of the imperfections of the human visual and auditory senses.
Perigee
The point of a satellite's orbit where it is closest to the Earth's surface.
Petal
Segment of a flyaway antenna.
PFD
Power flux density: a measure of the satellites illumination of the Earth's surface.
Phase noise
Phase interference in the wanted digital signal which can cause the digital signal to fail to be demodulated correctly.
Phase stability
Characteristic that is important in digital transmission components - lack of phase stability can cause the digital signal to fail to be demodulated correctly.
Phase-combiner
Multi-port microwave device which ensures that the individual outputs from two HPAs are combined together so that the outputs are added inphase.
Phase-locked loop
PLL: type of electronic circuit used to demodulate satellite signals.
Piece-to-camera
Where a reporter gives a news report face to camera.
Pixel
Smallest element that is discernible (quantified and sampled) in a picture.
Pixellation
Aberration of a digitally coded television picture where the individual digitally coded samples can be seen.
Pointing loss
Loss due to misalignment of boresight of antenna towards satellite, and movement of satellite within its station-kept 'box'.
Polarization
Geometric plane in which the electromagnetic signals are transmitted.
Pool
Grouping of newsgathering entities, usually for a limited period, to pool resources to cover a news event.
POP
Point of presence.
POR
Pacific Ocean Region: describes coverage area of a satellite.
Power density
Density of radiated power from an antenna, measured in W/m2 (mW/cm2).
Precipitation loss
Loss due to rain attenuating the signal, particularly in the Kuband, and further dispersing the signal as it passes through the drops of water.
Precipitation zone
To aid in calculating the effect of precipitation loss, the world is divided into precipitation zones or rain climatic zones, each of which has a numerical value defined by the ITU, used in the calculation of a link budget.
Pre-emphasis
Type of frequency-dependent level boosting/cutting or filtering.
Pre-emptible
Satellite service that may be interrupted or displaced by another, higher-priority service, typically (but not exclusively) during a satellite contingency situation.
PRI
Primary rate ISDN.
Primary rate ISDN
PRI: primary rate ISDN provides 30 64 kbps (B) data channels and 1 64 kbps (D) signalling channel.
PSK
Phase shift key modulation: digital phase modulation.
PSTN
Public Switched Telephone Network.
PTC
Piece-to-camera.
PTO
Public telecommunications operator; power take-off: where a generator may be driven through a vehicle's road engine and transmission system while the vehicle is at rest.
PTT
Post, telephone and telegraph administration: national telecommunications agencies directly or indirectly controlled by governments, in charge of telecommunications services in most countries of the world.
Pulse code modulation
PCM: time division modulation technique in which analogue signals are sampled and quantized at periodic intervals into digital signals - typically represented by a coded arrangement of 8 bits.