Internship Report
Muhammad Owais Mehmood
NUST-PNEC
Internee Pakistan CAA
Electronics Engineering Depot
23rd Jun to 13th Jul 2012
Pakistan Civil Aviation Authority
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List of contents
Introduction…………………………………………………………………………………………………3
Radar Central Workshop……………………………………………………………………………………4
Navigational Aids…………………………………………………………………………………………..9
HF (high frequency) section………………………………………………………………………………12
VHF/UHF section…………………………………………………………………………………………13
Telecom section…………………………………………………………………………………………...14
General electronics section………………………………………………………………………………..15
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Pakistan's Civil Aviation Authority (CAA) is a regulatory authority, whose responsibility is to oversee
and regulate all aspects of civil aviation in Pakistan. Nearly all civilian airports and aviation facilities in
Pakistan are owned and operated by the CAA. CAA's head office is situated in terminal 1 of Jinnah
International Airport in Karachi.
Pakistan Civil Aviation Authority is a Public sector autonomous body working under the Federal
Government of Pakistan through the Ministry of Defense. It was established on 7th December, 1982 as an
autonomous body. Prior to its creation, a Civil Aviation Department in the Ministry of Defense used to
manage the civil aviation related activities.
CAA is also a member of the International Civil Aviation Organization (ICAO).
Electronics Engineering Depot (EED)
Electronics engineering depot (EED) in Karachi is the central and the biggest facility of CAA all over
Pakistan with respect to electronics engineering services provided by the authority. EED covers all the
electronic equipments which provide aviation services all over Pakistan. The EED holds following major
functions at CAA:
Procurement of all new aviation equipments (Radars, Voice logging systems, ILS etc) and
thorough testing of each equipment after purchase.
Providing on field repair and maintenance facilities all over Pakistan through its trained
personnel.
Workshops for extensive repair facilities at EED in case the equipment could not be repaired at
site.
The EED is divided into sub sections, each dealing with the equipment of its own concern. These sections
are:
Radar central workshop (RCWS)
Navigational Aids section
VHF/UHF section
HF section
General electronics section
Telecom section
Each section has the test equipment and trained personnel to deal with the problems occurring in their
respective fields.
Our training program at EED was designed in such a way so that that we could understand the
functionality of each section. We spent the allocated time in each section and got familiar with the
functioning of equipment as well as the repairing tools used. Following is the short detail of each
section‘s equipment and operation.
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Radar Central Workshop (RCWS)
RADAR stands for ‗Radio detection and Ranging‘. Radar is an equipment which is used to detect objects
using ‗Radio Waves‘. It is a way to detect and study far off targets by transmitting a radio pulse in the
direction of the target and observing the reflection of the wave. It‘s basically radio echo.
In civil aviation radars are used to monitor and control commercial air traffic. A radar can provide
following information about a target which helps in managing the air traffic.
Target range
Target angles (azimuth & elevation)
Target size (radar cross section)
Target speed (Doppler)
Target features (imaging)
As far as civil aviation is concerned, the radars used can be divided into two main types:
Primary surveillance Radar
Secondary surveillance Radar
Primary surveillance Radar (PSR):
Primary Radar works on the principle in which the radar transmitter sends out a pulse of radio energy, of
which a very small proportion is reflected from the surface or structure of the target aircraft back to the
radar receiver.
The azimuth orientation of the radar antenna provides the bearing of the aircraft from the ground station,
and the time taken for the pulse to reach the target and return provides a measure of the distance of the
target from the ground station. The bearing and distance of the target can then be converted into a ground
position for display to the Air Traffic Controller. Target elevation (altitude) is not normally measured by
ATC primary radars. The advantage of Primary Surveillance Radar (PSR) is that it operates totally
independently of the target aircraft - that is, no action from the aircraft is required for it to provide a radar
return.
The disadvantages of PSR are that, firstly, enormous amounts of power must be radiated to ensure returns
from the target. This is especially true if long range is desired. Secondly, because of the small amount of
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energy returned at the receiver, returns may be easily disrupted due to such factors as changes of target
attitude or signal attenuation due to heavy rain. This may cause the displayed target to 'fade'.
PSR‘s are further divided into two categories based on the type of signal emitted by the radar:
Continuous wave Radar
Pulsed wave Radar
In a pulsed wave radar system the pulse modulated signal are used for transmission. Duplexer is used
to use common antenna for transmission & reception. It can indicate the range of target. It requires
comparatively higher transmitting power. The circuits used in this system are comparatively complicated.
The performance is not affected by presence of number of targets. It is some times used for the mapping
of the airport area.
On the other hand CW radar uses modulated or unmodulated continuous signals for transmission.
Circulator is used or separate antennas are used for transmission & reception. Simple CW RADAR can
not indicate the range. The Doppler frequency shift of echo signal is useful for indication device. It uses
lower transmitting power. The circuits are simpler. The performance is unaffected by stationary targets.
The system gets confused by presence of large number of targets.
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Specifications of the PSR used at JIAP
PSR Model: TA-10K
(Terminal Approach 10 cm Waveguide Klystron (Final Output Stage Power Amplifier))
(Frequency Band 2700 MHz to 2900 MHz)
Range (In Diversity Mode) = 98 NM at height of 30,000 feet
(When Both Channels are operational)
Peak Power (Per Transmitting Pulse) = 1.5 M Watts (maximum)
Peak Power (Per Transmitting Pulse) = 1.25 M Watts (operational)
Average Power (output) = 4 Kilo- Watts
Pulse Repetition Frequency = 666 Hz (operational)
Pulse Repetition Time Interval = 1.5 milliseconds (operational)
Pulse Repetition Frequency (optional) = 333 Hz (optional)
Operating Frequency Range = From 2700 MHz to 2900 MHz
Pulse Width = 1.7 Microseconds
Antenna Rotation Speed (High) = 10 Rpm
Antenna Rotation Speed (Low) = 5 Rpm
Standing Wave Ratio < 02
Range Resolution = 60 Meters (400 Nanoseconds)
Azimuth Resolution = 1.4 Degrees
Minimum Target Area to detect = 2 Square Meters (Minimum Radar Cross-Sectional
Area)
Secondary surveillance Radar (SSR):
The disadvantages of PSR led to the employment of another aspect of wartime radar
development. This was the Identification Friend or Foe (IFF) system, which had been developed as a
means of positively identifying friendly aircraft from enemy. The system which became known in civil
use as Secondary Surveillance Radar (SSR) relies on a piece of equipment aboard the aircraft known as a
'transponder'.
The transponder is a radio receiver and transmitter operating on the radar frequency. The target
aircraft's transponder responds to interrogation by the ground station by transmitting a coded reply signal.
The great advantages of SSR are three: firstly, because the reply signal is transmitted from the aircraft it is
much stronger when received at the ground station, thus giving the possibility of much greater range and
reducing the problems of signal attenuation; similarly, the transmitting power required of the ground
station for a given range is much reduced, thus providing considerable economy; and thirdly, because the
signals in each direction are electronically coded the possibility is offered to transmit additional
information between the two stations.
The disadvantage of SSR is that it requires a target aircraft to carry an operating transponder.
Thus SSR is a 'dependant' surveillance system. For this reason, PSR will operate in conjunction with SSR
in certain areas for the foreseeable future so that 'non-cooperating' targets, such as some light aircraft, can
be detected.
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Modes of SSR
SSR has several modes of operation.
The basic civil mode is Mode A. In this mode the aircraft's transponder provides positive aircraft
identification by transmitting a four-digit code to the ground station. The code system is octal;
that is, each of the code digits may be any of the numbers 0-7. There are thus 4096 possible four-
digit codes.
Another principal SSR mode currently used is Mode C. In this mode the aircraft's altitude,
derived from on-board instruments, is transmitted to the ground station in addition to the identity.
A further mode, Mode S (or 'Mode Select'), is also used. Aircraft equipped with transponders
supporting this mode are assigned a permanent identification which can be selectively addressed
by the ground radar. This reduces problems of garbling between SSR returns from aircraft in
close proximity. Mode S also offers a wider range of data to be transmitted, including potentially
an uplink of data from the ground station to the aircraft although this capability is presently not
used in Pakistan.
Additional SSR Modes are used by military aircraft.
Specifications of secondary surveillance radar used at JIAP
SSR Model: RSM-870 (Radar Secondary Mono Pulse)
Range (One Way) = 200 NM (1 NM = 1852 Meters)
Interrogation Frequency = 1030 MHz
Reply from Transponder = 1090 MHz (This is not part of SSR Equipment)
Power Consumption = 600 Watts
Pulse Width = 0.8 Microseconds
Capacity = 300 Aircrafts (Processing)
Operating band = L – Band
Transmitter output Power (High) = 1.5 K Watts
SSR Modes (Available) = Alpha (Identity) & Charlie (Altitude)
For repair and maintenance of these radars and other radars installed all over Pakistan following
equipments are present in the RCWS:
1. AFIT-1500 In Circuit digital IC Tester (Excluding RAM & EPROM ICs) up to 24 Pins Digital /
TTL ICs only.
2. Tracker ―Huntron=5100DS‖ (Hardware change Cold Tester)
3. Micro-System Trouble Shooter.
4. Frequency Counter
5. Power Meter.
6. Synthesizer / Level Generator.
7. VHF Switch.
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8. Relay Actuator
9. System Power Supply of Hewlett Packard.
10. Combinational System S-645 Programmable Fault Finder of Schlumberger. (Unserviceable)
11. Curve Tracer. Tektronix-571
12. EPROM Programmer ―Unisite‖
13. TEST BENCH OF RICS TXM-4200 SYSTEM
14. Chip Master Compact (Digital IC Tester)
15. Linear Master Compact (Analogue ICs Tester)
16. Component Analyzer (Up to 3-Pins Components Tester)
17. Relative Humidity & Temperature Tester.
18. ROBIN Microwave Leakage Tester.
19. BK Precision Auto Ranging Capacitance Meter, Model 830A
20. BK Precision Inductance Meter, Model # 875B
21. Fluke Scope Meter, Model # 199C
22. Fluke Multimeters, Model # 187
23. Toolkit Xcelite TC-100ST
24. Soldering Station ―Weller‖
25. Huntron Pro-Track-I Model 20
26. DATAMAN Universal EPROM Programmer
27. De-Soldering Station ―Weller‖ .
28. Huntron Scanner-I (part of Tracker)
29. Agilent Digital Colour LCD Oscilloscope
30. 6-GHz Spectrum Analyzer Model FSL6
31. Battery Load Tester (200A)
32. ERSA Infra-Red Rework Station IR/PL-550A
A secondary surveillance radar antenna mounted on primary radar antenna.
Visit to JIAP Area Control Centre:
During the internship period we visited the Area control centre which hosts the primary and secondary
radars as well as the air traffic management structure. People who mange air traffic through radar data are
called Air Traffic Controllers or ATCs. Radars are installed in different parts of Pakistan and the data
from other radars is sent to the Area control centre through a satellite link. This data contains video as
well as audio. There are different desks in Area control centre each of which manages traffic in the
assigned area.
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Navigational Aids Section
The department of Navigational aids deals with equipment used in en route navigation and terminal
navigation.
En Route Navigation equipment: When the plane is successfully in the air after take off then the navigational aids used to guide the aircraft
to its destination are known as En route navigation. The most basic equipment used for en route
navigation are:
NDB (Non directional beacon)
VOR (Very high frequency Omni-directional Ranging)
DME (distance measuring equipment)
NDB:
Non-Directional Beacons (NDBs) are today the most common type of radio beacon found because of
their simplicity and relative cheapness. NDBs are basically a simple radio transmitter which radiates a
signal equally in every direction (hence 'non-directional'). This signal is modulated with a Morse code
identity signal.
This allows suitably equipped aircraft to 'home' on the beacon, bringing the
aircraft to a position overhead. From there, the aircraft can either track to
another beacon, or perform an instrument approach procedure using the NDB for
lateral guidance.
In Pakistan NDB operates at 190 – 525 Khz.
Models of NDBs. used by CAA are:
Aerocom 5401, 5034
Nautel ND-500, ND-2000
Southern Avionics SS - 1000
VOR:
VOR, short for VHF Omni directional radio range, is a type of radio navigation system for aircraft. A
VOR ground station broadcasts a VHF radio composite signal including the station's identifier, voice (if
equipped), and navigation signal. The identifier is Morse code. The voice signal is usually station name,
in-flight recorded advisories, or live flight service broadcasts. The navigation signal allows the airborne
receiving equipment to determine a magnetic bearing from the station to the aircraft (direction from the
VOR station in relation to the Earth's magnetic North at the time of installation). VOR stations in areas of
magnetic compass unreliability are oriented with respect to True North. This line of position is called the
"radial" from the VOR. The intersection of two radials from different VOR stations on a chart provides
the position of the aircraft.
D-VOR are for hilly area
C-VOR are for plane area
Comparison between D- VOR & C-VOR:
Doppler VOR beacons are inherently more accurate than Conventional VORs because they are more
immune to reflections from hills and buildings. The variable signal, in a DVOR, is the 30Hz FM signal.
In a CVOR it is the 30Hz AM signal. If the AM signal from a CVOR beacon, bounces off a building or
hill, the aircraft will see a phase that appears to be at the phase centre of the main signal and the reflected
signal, and this phase centre will move as the beam rotates. In a DVOR beacon, the variable signal will, if
reflected, seem to be two FM signals of unequal strengths and different phases. Twice per 30Hz cycle, the
instantaneous deviation of the two signals will be the same, and the phase locked loop will get (briefly)
confused. As the two instantaneous deviations drift apart again, the phase locked loop will follow the
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signal with the greatest strength, which should be that due to the line-of-sight signal. This will depend on
the bandwidth of the output of the phase comparator in the aircraft. Hence some reflections can cause
minor problems, but these are usually about an order of magnitude less than in a CVOR beacon.
Models of VOR used by CAA are:
C-VOR: Wilcox 585B
D-VOR: Thomson-CSF 512-C, 512-D
DME:
Distance measuring equipment (DME) is a transponder-based radio navigation technology that measures
distance by timing the propagation delay of VHF or UHF radio signals. Aircraft use DME to determine
their distance from a land-based transponder by sending and receiving pulse pairs - two pulses of fixed
duration and separation. The ground stations are typically co-located with VORs. A typical DME ground
transponder system for en-route or terminal navigation will have a 1 kW peak pulse output on the
assigned UHF channel.
In Pakistan DME operates at 962 – 1213 Mhz
Models of VORs used by CAA are: Wilcox 596B
Thomson-CSF 712
Terminal Navigation: The navigation techniques used to help the aircraft in landing is known as terminal navigation. The whole
set of equipment used in the process is known as Instrument Landing System (ILS).
Components of ILS
An instrument landing system (ILS) is a ground-based instrument approach system that provides
precision guidance to an aircraft approaching and landing on a runway, using a combination of radio
signals. These informations are:
Guidance information: the localizer and glide slope.
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Range information: the outer marker (CM) and the middle marker (MM) beacons.
Visual information (high-intensity lighting arrays to enable a safe landing) PAPI approach lights,
touchdown and centerline lights, runway lights
Localizer:
The localizer signal provides information to guide the aircraft to the centerline of the runway
The localizer antenna is located at the far end of the runway.
The approach course of the localizer is called the front course.
The course line in the opposite direction to the front course is called the back course.
The localizer signal normally usable 18 NM from the field.
The Morse code Identification of the localizer consists of a three-letter.
Principle of Operation of Localizer: A localizer antenna array is normally located beyond the departure
end of the runway and generally consists of several pairs of directional antennas. Two signals are
transmitted on one out of 40 ILS channels between the carrier frequency range 108.10 MHz and
111.95 MHz (with the 100 kHz digit always odd). One is modulated at 90 Hz, the other at 150 Hz and
these are transmitted from separate but co-located antennas. Each the left of the runway centerline, the
other to the right antenna transmits a narrow beam, one slightly to the left of the runway centerline, the
other to the right.
Glide Slope: A glide slope (GS) or glide path (GP) antenna array is sited to one side of the runway
touchdown zone. The GP signal is transmitted on a carrier frequency between 329.15 and 335 MHz using
a technique similar to that of the localizer. The centerline of the glide slope signal is arranged to define a
glide slope of approximately 3° above horizontal (ground level). The beam is 1.4° deep; 0.7° below the
glide slope centerline and 0.7° above the glide slope centerline.
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TDME:
Terminal Distance Measuring Equipment (TDME) gives the information of distance from touch down
point. Terminal DME, referred to as a TDME in navigational charts, is a DME that is designed to provide
a 0 reading at the threshold point of the runway, regardless of the physical location of the equipment. It is
typically associated with Glide Slope.
Marker Beacons:
Marker beacons are used to alert the pilot by audio and visual cues. It gives the distance from threshold
point on the extended center line of the runway, at a particular height. ILS contains three marker beacons:
inner, middle and outer. The inner marker is used only for Category II operations. The marker beacons are
located at specified intervals on the extended center line. All marker beacons operate on a frequency of 75
MHz.
Visit to Navigational Aids section and ATC control Tower:
During the internship we visited the navigational aids section at CAA headquarters and saw the
equipment currently being used for terminal and en route navigation. We went to the Equipment control
room which holds the communication equipment. We also got familiar with the Aeronautical message
handling system.
ATS Message Handling System (AMHS) also known as Aeronautical Message Handling System is a
standard for aeronautical ground-ground communications (e.g. for the transmission of NOTAM, Flight
Plans or Meteorological Data).
HF section
High frequency (HF) radio provides aircraft with an effective means of communication over long distance
oceanic and trans-polar routes. In addition, global data communication has recently been made possible
using strategically located HF data link (HFDL) ground stations. An aircraft HF radio system operates on
spot frequencies within the HF spectrum.
In the HF range (3 MHz to 30 MHz) radio waves propagate over long distances due to reflection from the
ionized layers in the upper atmosphere. Due to variations in height and intensities of the ionized regions,
different frequencies must be used at different times of day and night and for different paths. There is also
some seasonal variation (particularly between winter and summer). Propagation may also be disturbed
and enhanced during periods of intense solar activity. The upshot of this is that HF propagation has
considerable vagaries and is far less predictable than propagation at VHF.
HF section deals with the equipment of direct communication in Long Range, providing
maintenance repairing and upgrading of HF communication equipments, for four
purposes:
• Ground to Air Domestic
• Ground to Ground Domestic
• Ground to Air International
• Ground to Ground International
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Presently HF RT is used as standby for ground to air communication, incase of Extended VHF failure. It
is also used for communication with the FIRs of Lahore, Kabul, Bombay and Delhi
HFRT(day) 10018 KHz 5658 KHz
HFRT(night) 3467 KHz 5658 KHz
HF SSB is used for ground to ground communication between CAA stations throughout the country.
VHF/UHF Section
This section deals with all the equipments of VHF/UHF used for the communication between Air
traffic Control to the plane or in other words ground to air communication. The maintenance of all the
VHF/UHF equipments from all over Pakistan comes under this department. There are various types of
antenna used in Communication of VHF/UHF, like whip antenna, long wire antenna, umbrella antenna,
half and full dipole antenna, VHF extended antenna etc.
Whereas, the general range of Frequencies used in CAA is from 118MHZ to 136 MHz.
Frequencies used by Civil Aviation Authority for different kind of Purposes are:
COMMUNICATORS MAIN(MHz) STANDBY (MHZ)
Tower controller 118.3 118.8
Ground controller 121.6 118.4
Surface frequency 121.8 123.0
Approach frequency 125.5 121.3
Radar frequency 123.3 127.3
VHF extended range 128.3 133.2
VHF emergency frequency 121.5 -
Since the range of VHF and UHF communication has line of sight restriction i.e. the receiver and
transmitter must be seeing each other for proper communication. This imposes a restriction over the usage
of VHF and UHF. However due to high quality communication in VHF and UHF band another technique
has been introduced which is known as extended VHF.
In extended VHF signals can be transmitted to far off places using satellite. The voice signal is
sent to the satellite through the up link and the satellite transmits it back to the destination station. Here
again the voice signal is transmitted in VHF band. Although this induces a delay in communication but
with modern equipment this delay is very small.
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Latest VHF/UHF Equipments used by CAA are:
JOTRON TR-810 Multi purpose VHF/AM Transceiver
10W output power
Detachable front panel
Automatic muting facility
Output for voice-recording
Frequency range: 118-137 MHz
DC voltage range from 10 to 28V
25kHz/8.33kHz channel separation(selectable)
Front or rear connection for microphone input
A bright and clear graphical display for easy readout
Fast recall of 3 present channels via dedicated buttons
Built-in loudspeaker with possibilities for an external loudspeaker Rohde & Schwarz
R&S®Series4200(Software Defined VHF & UHF Radios)
VHF frequency range from 112 MHz to 156 MHz
UHF frequency range from 225 MHz to 400 MHz
Output power of 50 W for VHF and UHF
8.33/25 kHz channel spacing for VHF
8.33/12.5/25 kHz channel spacing for UHF
Serial interface for controlling automatic filters
Automatic main/standby operation
USB service port for configuration and software downloads
Remote control and remote monitoring via Ethernet interface
Best signal selection in the receiver
Suitable for data transmission in line with VDL mode 2 standard
In-band signaling for push-to-talk (PTT) and squelch (SQ) with the capability to set different tones
Telecom Section
Telecom section was originally developed to look after and maintain the intercom system within CAA but
now it is replaced by the modern PBX system.
PBX stands for private branch exchange. It is a network of telephones within an organization
and is also extended to the public telephone system or PSTN. Organizations that have more than a few
phones usually have an internal switching mechanism that connects the internal phones to each other and
to the outside world. A PBX is like a miniature Central Office switching system designed for a private
institution. A PBX usually has a console station that greets outside callers and connects them to internal
extensions.
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A PBX is composed of three major elements.
1. Common equipment (a processor and a switching matrix)
2. CO trunks
3. Station lines
Besides this telecom section also takes care of the fax machines of CAA.
General Electronics Section
This section deals with all the rest of the equipment that comes into use of CAA. However the
major equipment comes from the following departments
DVLS (digital voice logging systems)
PA (public addressing) systems
FIDS (flight information display systems)
DVLS:
Formerly VLS was used for recording all types of conversations, works on the analog principle of
magnetic tape recording. The VLS tape can record a day‘s recording and has to be replaced the other day.
The system is being replaced by the DVLS. It is the most important and major equipment with which GE
deals. This is the Latest machine use for the recording all types of conversation. recording stuff is
reserved for 30 days in DVD-RAM . The model of DVLS
used by CAA is Marathon Evolution.
ASC MARATHON EVOLUTION
World‘s First Linux-based communications recorder
Multimedia recording from, Traditional telephony
and radio, VoIP (Voice over IP), Trunked radio
Fax data, Screen data
The system can be configured to record, live monitor and archive communications at one location
and to provide
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Search and replay facilities locally or via LAN / WAN, Intranet or Internet.
Analog inputs: 4 ... 192 channels
Digital inputs: 4 ... 120 channels or mixed configuration of analog / digital / VoIP
VoIP: 4 ... 32 channels (active) 4 ... 120 channels (passive)
PA systems:
A public address system (PA system) is an electronic amplification system with a microphones,
preamplifiers and/or signal routers mixer, which allows variation in sound levels, amplifier to increase the
sound and loudspeakers placed in convenient locations around the broadcasting area, used to reinforce a
sound source. The user speaks into a microphone, and the sound is transmitted through connected cables
to the area surrounding the speakers.
FIDS:
Flight Information Display Systems (FIDS) help improve communications and keep passengers
constantly informed of travel information. To manage the heavy and ever increasing passenger traffic, an
airport in the Middle-East needed terminal-wide FIDS that broadcasted information from a constantly
updated database to numerous multimedia displays placed strategically throughout passenger facilities.
These indoor displays needed to supply timely information regarding flight arrivals/departures, gate
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assignments, waiting hall locations, baggage area assignments, and weather forecasts—as well as
entertainment and advertising content. Considering the airport handles millions of passengers per year, a
reliable mission-critical solution was needed. Any potential onsite technical problems could cause serious
consequences that might disrupt the operation of the airport.
System Characteristics
1) Diversification of contents and formats: multiple media formats, including images, texts, Flash, MPEG
video, etc.
2) Diversification of page display: pages for flight and public information are displayed alternately. The
latter is displayed in shorter time.
3) Strictly obey the rules of display according to the time order of flights.
4) Continuity of display: when the video public information and flight information are displayed on the
same page, the existing video display will not be interrupted due to the page refresh caused by
dynamic modification of flight information.
5) Public information display is to demonstrate the information related to airport operating issues
including lost notice, urgent notice, change of boarding gates and delay of flight.