PROJECT REPORT OF INDUSTRIAL TRAININGATAIPORT AUTHORITY OF INDIA

Submitted by: - Ashwini kumar 11015002711 CSE - II

ACKNOWLEDGEMENT

It was a great privilege for me to get my training at Air Traffic Control (ATC) under the Airports Authority of India (AAI).

This report describes the training that I underwent, in the month of July 2013 at Air Traffic Control (ATC) under Airport Authority of India (AAI).It was completed, keeping in mind the course curriculum as per the university requirements.

I would like to express our sincere gratitude to the all the people who have helped and supported us throughout. We are deeply indebted to Mr. S.K Tomar for organizing our training program, efficiently and providing us valuable resources and also for their cooperation and willingness to share their expertise and knowledge and to devote their precious time to discuss related topics. We would also like to thank Mr. Anshul Ranjan, Mr. Anup (NAV AIDS unit), Mr. Abhishek, Mr. SK Sharma (Automation Unit / Assistant manager), and Mrs. Renu Singh (VHF unit / Manager) for giving us an opportunity to get a training exposure at their units. In the last but not the least us grateful appreciation is also extended to our fellow batch-mates for their support in developing this project.

The help and co-operation extended by the staff of ATC is fully acknowledged. We thoroughly enjoyed our entire training program and would like to thank everyone at ATC for their guidance and support.

CONTENTS

S. NoTOPICPAGE No.

1ACKNOWLEDGEMENT

1

2INTRODUCTION3

3AIR TRAFFIC CONTROL3

4ICAO4

5ORGANISATIONS5

6ATM6

7ATS ORG.

7

8NAV AIDS 9

9Overview9

10Localizer 11

11Localizer working12

12Glide path13

13Glide path working14

14DME15

15Marker17

16NDB18

17VOR19

18CVOR & DVOR

20

19AUTOMATION SYSTEM21

20Functional subsystem24

21System description25

22Brief description26

23Packet switching29

24RADAR31

25VHF37

26Modulation42

27DVR44

28SECURITY EQUIPMENTS45

INTRODUCTION

AIR TRAFFIC CONTROL Air traffic control (ATC) is a service provided by ground-based controllers who direct aircraft on the ground and in the air. The primary purpose of ATC systems worldwide is to separate aircraft to prevent collisions, to organize and expedite the flow of traffic, and to provide information and other support for pilots when able. In some countries, ATC may also play a security or defense role (as in the United States), or be run entirely by the military (as in Brazil). In addition to its primary function, the ATC can provide additional services such as providing information to pilots, weather and navigation information and NOTAMs (Notices to Airmen). In many countries, ATC services are provided throughout the majority of airspace, and its services are available to all users (private, military, and commercial).

AIRSPACE Airspace means the portion of the atmosphere controlled by a particular country on top of its territory and territorial waters or, more generally, any specific three-dimensional portion of the atmosphere. Controlled airspace exists where it is deemed necessary that air traffic control has some form of positive executive control over aircraft flying in that airspace. Uncontrolled airspace is airspace in which air traffic control does not exert any executive authority, although it may act in an advisory manner.

Airspace may be further subdivided into a variety of areas and zones, including zones where there are either restrictions on flying activities or complete prohibition of flying activities. By international law, the notion of a country's sovereign airspace corresponds with the maritime definition of territorial waters as being 12 nautical miles (22.2 km) out from a nation's coastline. Airspace not within any country's territorial limit is considered international, analogous to the "high seas" in maritime law. However, a country may, by international agreement, assume responsibility for controlling parts of international airspace, such as those over the oceans. For instance, the United States provides air traffic control services over a large part of the Pacific Ocean, even though the airspace is international. However, there is no international agreement on the vertical extent of sovereign airspace. Depending on the type of flight and the class of airspace, ATC may issue instructions that pilots are required to follow, or merely flight information (in some countries known as advisories) to assist pilots operating in the airspace. In all cases, however, the pilot in command has final responsibility for the safety of the flight, and may deviate from ATC instructions in an emergency. Air traffic controllers are people who operate the air traffic control system to expedite and maintain a safe and orderly flow of air traffic and help prevent mid-air collisions. They apply separation rules to keep each aircraft apart from others in their area of responsibility and move all aircraft safely and efficiently through their assigned sector of airspace. Because controllers have a demonstrably large responsibility while on duty, the ATC profession is often regarded as one of the most difficult jobs today, and can be notoriously stressful.

INTERNATIONAL CIVIL AVIATION ORGANISATION (ICAO) The International Civil Aviation Organization (ICAO), an agency of the United Nations, codifies the principles and techniques of international air navigation and fosters the planning and development of international air transport to ensure safe and orderly growth. Its headquarters are located in the Quartier International of Montreal, Canada. The ICAO Council adopts standards and recommended practices concerning air navigation, its infrastructure, Flight inspection, prevention of unlawful interference, and facilitation of border-crossing procedures for international civil aviation. In addition, the ICAO defines the protocols for air accident investigation followed by transport safety authorities in countries signatory to the Convention on International Civil Aviation, commonly known as the Chicago Convention. AIR TRAFFIC CONTROL IN INDIA In every country, ICAO annexure decides who is responsible for air traffic services. In India, the DGCA i.e. the director general of civil aviation is responsible for all the air traffic services. It used to operate directly in providing these services until 1995. The Airports Authority of India has been providing these services on the behalf of DGCA. The Airports Authority of India (AAI) was formed on 1st April 1995 by merging the International Airports Authority of India and the National Airports Authority with a view to accelerate the integrated development, expansion and modernization of the operational, terminal and cargo facilities at the airports in the country conforming to international standards. Presently it is owned by the Government of India.

ORGANISATIONFUNCTIONS To control and manage the entire Indian airspace (excluding the special user airspace) extending beyond the territorial limits of the country, as accepted by ICAO. Provisioning of Communication and Navigational aids viz. ILS, DVOR, DME, Radar, etc. To Design, Construct, Operate and Maintain International Airports, Domestic Airports, and Civil Enclaves at Defence Airports. Development and Management of International Cargo Terminals. Provisioning of Passenger Facilitation and Information System. Expansion and Strengthening of Operational areas viz. Runways, Apron, Taxiways, etc. Provisioning of Visual Aids.

AIR TRAFFIC MANAGEMENT An information service and alerting service are the basic levels of air traffic service, providing information pertinent to the safe and efficient conduct of flights and alerting the relevant authorities should an aircraft be in distress. These are available to all aircraft through an FIR. FLIGHT INFORMATION REGION (FIR) The airspace of the world has been divided into homogeneous regions called FIRs. A Flight Information Region (FIR) is an aviation term used to describe airspace with specific dimensions, in which a Flight Information Service and an alerting service are provided. It is the largest regular division of airspace in use in the world today. Any portion of the atmosphere belongs to some specific FIR. Smaller countries' airspace is encompassed by a single FIR; larger countries' airspace is subdivided into a number of regional FIRs. Some FIRs may encompass the territorial airspace of several countries. Oceanic airspace is divided into Oceanic Information Regions and delegated to a controlling authority bordering that region. The division among authorities is done by international agreement through ICAO. There is no standard size for FIRs; it is a matter for administrative convenience of the country concerned. The FIR is responsible for providing air traffic services to all the flights that are: Entering (overhead) Leaving (overhead) Taking off Landing In India, there are five such FIRs namely: Delhi Mumbai Chennai Calcutta Guwahati

The region of airspace over which an FIR is responsible for providing air traffic services is broadly classified as: Area Approach Tower

Media links to enable the effective management of air traffic services in the Delhi FIR. ATS ORGANISATION AIR TRAFFIC MANAGEMENT can be broadly categorized as CNS ATC. CNS: Communication, Navigation and Surveillance which are the three basic facilities which aid civil aviation. Thus, CNS is the building block of ATM. COMMUNICATION is a process of transferring information from one source to another. Communication is commonly defined as "the imparting or interchange of thoughts, opinions, or information by speech, writing, or signs". Communication can be perceived as a two-way process. But in civil aviation it is one-way process. At any time either the controller can speak or the pilot can speak. COMMUNICATION in civil aviation can be further classified as : Ground to ground: This enables various stations in the AFTN (aeronautical fixed telecommunications network) to communicate via low or high speed links. Various messages containing important information are exchanged. The communication is based on store and forward principle. Ground to Air: This includes all the communication between the controllers and the pilot. It may include voice communication or DATIS or any other form of messages. Ground to Air communication generally uses either VHF of HF frequencies. Communication takes place through transmitters and receivers installed on the ground as well as on board the aircraft. VHF and HF are used for voice communication. VHF transmitters have short range while HF can be used for communicating over long distances. Air to Air: This may include communication between the pilots of two aircrafts in the air. Such type of communication also uses VHF and HF frequencies. NAVIGATION is the process of reading, and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks. Navigation in civil aviation was earlier accomplished by means of various equipments such as NDB, ILS, DVOR, and DME. NDB is the oldest known navigational tool. It works on the basic principle of the magnetic compass. Nowadays, advanced equipments such as the VOR and DME are used as navigational aids. DVOR is the directional very high frequency Omni radio range which measures the azimuth angle with respect to the north. It radiated lines across 360 deg each of which are spaced 1 deg apart. There may be several VORs installed in an FIR. When an aircraft comes overhead a VOR it gives the pilot the direction it must move in order to reach the next VOR on the air route to its destination. ILS is the instrument landing system which helps the aircraft to land safely. DME gives the slant distance of the aircraft. SURVEILLANCE is the monitoring of the behavior of a person or group of people, often in a surreptitious manner. The word surveillance is commonly used to describe observation from a distance by means of electronic equipment. In civil aviation surveillance equipment is installed in each airport to monitor the movement of all the aircrafts within its region of operation. Primary and secondary radar are used to aid surveillance in civil aviation. ATC Air Traffic Control: As explained earlier is a service provided by air traffic controllers on the ground to all the aircrafts in air and on the ground. The air traffic controllers are able to maintain direct contact with the pilots and guide them to move forward towards their destination. Hence, ATC uses all the facilities provided by CNS. NAVIGATION AIDS

OVERVIEW

Early pilots looked out of their open cockpits for roads, rail lines, and airports to find their way in daytime flight. Pilots watched the horizon to make sure they were flying with the aircraft's nose and wings in the proper position relative to the ground, called altitude. As airmail pilots began flying at night and in all kinds of weather in the early 1920s, new equipment helped pilots navigate and maintain aircraft altitude when they could not see the ground. So at that time it is not possible to take off/land in low visibility due to many reason (eg.fog, rain, or blowing snow, and it consists of more than one component).

Navigation aids (Nav-aids) were developed in 1926, for use inside the aircraft and also to guide the pilots from the ground. The NAVAIDS unit is responsible for providing and maintaining all the navigational aids required for providing air traffic services.

In NAV-AIDS there is 2 type of landing system based on visibility:-

Landing categories

The approach and landing are the most dangerous part of the flight. When the pilot has sufficient visibility, he is allowed to perform the landing under Visual Flight Rules (VFR). However, when visibility is reduced (e.g. due to bad weather), the pilot has to use Instrument Flight Rules (IFR): he has to land, using only his instruments. The International Civil Aviation Organization (ICAO) has defined three categories of visibility.These categories are based on the decision height (DH) and the runway visual range (RVR). The DH is the height above the runway at which the landing must be aborted, if the runway is not in sight. The RVR is the visibility at the runway surface. The three categories are as follows.

Cat I DH > 200 ft and RVR >2600 ft. Cat II DH > 100 ft and RVR >1200 ft. Cat III DH < 100 ft and RVR RS 422. Because of short range of RS 232[15.24 m], data is passed to workstation from it again converted back to RS 422 -> RS 232.Transition server is only to divide the data.

3 CGP:-

Here router is connected back to back, so that if any router fails working will remain continuous.

RADAR

Radaris an object detection system which usesradio wavesto determine the range, altitude, direction, or speed of objects. The word Radar is an abbreviation for Radio detection and Ranging. It can be used to detectaircraft, ships,spacecraft, guided missiles,motor vehicles,weather formations, and terrain. It cannot resolve details or color. The radar dish or antenna transmits pulses of radio waves ormicrowaveswhich bounce off any object in their path. The object returns a tiny part of the wave's energy to a dish or antenna which is usually located at the same site as the transmitter. The highest frequencies gave the most accurate results. Higher frequencies produce the best echoes, make it possible to detect smaller targets and permit the use of smaller antennas. High tech radar systems are associated withdigital signal processingand are capable of extracting useful information from very high noise levels.

RADAR PRINCIPLEThe RADAR antenna illuminates the target with a microwave signal, which is then reflected and picked up by a receiving device. The electrical signal picked up the receiving antenna is called echo or return. The RADAR signal is generated by a powerful transmitter and received by a highly sensitive receiver.

BLOCK DIAGRAM OF SIMPLE RADAR

The elemental radar system consists of a transmitter unit, an antenna for emitting electromagnetic radiation and receiving the echo signal, an energy detecting receiver and a processor.

As shown in the above figure, a portion of the transmitted signal is intercepted by a reflecting Object (target) and is reradiated in all directions. The antenna collects the returned energy in the backscatter direction and delivers it to the receiver. The distance to the receiver is determined by measuring the time taken for the electromagnetic signal to travel to the target and back.IMPROVED RADARA modified block diagram is shown in the given figure which has another important block called the duplexer.The functions of a duplexer are:1. To isolate the transmitter and receiver during transmission and reception.2. To protect the receiver from high power transmitter and3. To help use a single transmitter/receiver antenna.

RADAR SIGNAL PROCESSING1. Distance measurement Transit timeOne way to measure the distance to an object is to transmit a short pulse of radio signal (electromagnetic radiation) and measure the time it takes for the reflection to return. The distance is one-half the product of the round trip time (because the signal has to travel to the target and then back to the receiver) and the speed of the signal. Since radio waves travel at thespeed of light, accurate distance measurement requires high-performance electronics. In most cases, the receiver does not detect the return while the signal is being transmitted. Through the use of a duplexer, the radar switches between transmitting and receiving at a predetermined rate. A similar effect imposes a maximum range as well. In order to maximize range, longer times between pulses should be used, referred to as a pulse repetition time, or its reciprocal, pulse repetition frequency.

Frequency modulationAnother form of distance measuring radar is based onfrequency modulation. Frequency comparison between two signals is considerably more accurate, even with older electronics, than timing the signal. By measuring the frequency of the returned signal and comparing that with the original, the difference can be easily measured. Since the signal frequency is changing, by the time the signal returns to the aircraft the transmit frequency has changed. The amount of frequency shift is used to measure distance. The measure of the amount of frequency shift is directly proportional to the distance traveled. That distance can be displayed on an instrument, and it may also be available via the transponder. A further advantage is that the radar can operate effectively at relatively low frequencies. This was important in the early development of this type when high frequency signal generation was difficult or expensive.

2. Speed measurementSpeedis the change in distance to an object with respect to time. Thus the existing system for measuring distance, combined with a memory capacity to see where the target last was, is enough to measure speed. If the transmitter's output is coherent (phase synchronized), there is another effect that can be used to make almost instant speed measurements (no memory is required), known as theDoppler Effect. The Doppler Effect is only able to determine the relative speed of the target along the line of sight from the radar to the target. Any component of target velocity perpendicular to the line of sight cannot be determined by using the Doppler Effect alone, but it can be determined by tracking the target'sazimuthover time.

TYPES OF RADARPRIMARY RADAR: Primary radar is a type of radar that can detect and report the position of anything that reflects its transmitted radio signals including, depending on its design, aircraft, birds, weather and land features. For air traffic control purposes this is both an advantage and a disadvantage. Its targets do not have to co-operate, they only have to be within its coverage and be able to reflect radio waves, but it only indicates the position of the targets, it does not identify them. When primary radar was the only type of radar available, the correlation of individual radar returns with specific aircraft typically was achieved by the Controller observing a directed turn by the aircraft. Primary radar is still used by ATC today as a backup/complementary system to secondary radar, although its coverage and information is more limited.

PRIMARY SURVEILLANCE RADAR IN USE

SECONDARY RADAR: Secondary surveillance radar(SSR)is aradarsystem used inair traffic control(ATC), that not only detects and measures the position of aircraft i.e. range and bearing, but also requests additional information from the aircraft itself such as its identity and altitude. Unlike primary radar systems that measure only the range and bearing of targets by detecting reflected radio signals, SSR relies on targets equipped with a radartransponder that replies to each interrogation signal by transmitting a response containing encoded data. SSR relies on the same equipment as PSR with one exception that each target must be equipped with a transponder. Pulses transmitted by SSR are much weaker than PSR because they do not need to be detected as reflectionsLimitations of Secondary Radar Since all aircraft will reply to SSR when it is detected the replies can sometimes merge together meaning traffic can be detected in the wrong position or its signal can be superimposed on another resulting in the traffic disappearing entirely. This process is called Garbling. Further to these problems traffic within 2nm of each other can sometimes get their responses intertwined this results in aircraft swapping data tags. While traffic is being interrogated by one ground signal it cannot reply to another request this means that responses to second RADAR heads can be delayed by up to 0.1s resulting in further inaccuracies. SSR requires traffic to have a transponder installed and functional. Using SSR alone produces an incomplete picture as traffic may be permitted to operate within airspace without a transponder.

L BAND RADARThis frequency band (1 to 2GHz) is preferred for the option of long-range air-surveillance radar out to 250N (approx. 400 km).They transmit pulses with high power, broad bandwidth and an intra pulse modulation often .Due to the curvature of the earth the achievable maximum range is limited for target flying with low altitude. These objects disappear very fast behind the radar horizon. In air traffic management (ATM) long-range surveillance radars like the Air Route Surveillance Radar (ARSR) works in this frequency band. Coupled with mono pulse secondary surveillance radar (MSSR) they use a relatively large, but slower rotating antenna. The designator L Band is a good as mnemonic rhyme as large antenna or long range.

S-BAND RADARS band radarsoperate on a wavelength of 8-15 cm and a frequency of 2-4 GHz. Because of the wavelength and frequency, S band radars are not easily attenuated. This makes them useful for near and far range weather observation. Special Airport Surveillance Radar are used at airport to detect and display the position of aircraft in the terminal area with a medium range up to 50-60NM(APPROX. 100KM).An ASR detect aircraft position and weather condition in the vicinity of civilian and military airfields. The designated S Band is a good as mnemonic rhyme as smaller antenna or shorter range. The National Weather Service (NWS) uses S band radars on a wavelength of just over 10 cm. The drawback to this band of radar is that it requires a large antenna dish and a large motor to power it. It is not uncommon for an S band dish to exceed 25 feet in size.

VERY HIGH FREQUENCY (VHF)

BASIC COMMUNICATION SYSTEM

Introduction: Transmitter, Receiver & Channel

Communication is the process of sending, receiving and processing of information by electrical means. It started with wire telegraphy in 1840 followed by wire telephony and subsequently by radio/wireless communication. The introduction of satellites and fiber optics has made communication more widespread and effective with an increasing emphasis on computer based digital data communication. In Radio communication, for transmission information/message are first converted into electrical signals then modulated with a carrier signal of high frequency, amplified up to a required level, converted into electromagnetic waves and radiated in the space, with the help of antenna. For reception these electromagnetic waves received by the antenna, converted into electrical signals, amplified, detected and reproduced in the original form of information/message with the help of speaker.

Transmitter

Unless the message arriving from the information source is electrical in nature, it will be unsuitable for immediate transmission. Even then, a lot of work must be done to make such a message suitable. This may be demonstrated in single-sideband modulation, where it is necessary to convert the incoming sound signals into electrical variations, to restrict the range of the audio frequencies and then to compress their amplitude range. All this is done before any modulation.

In wire telephony no processing may be required, but in long-distance communications transmitter is required to process, and possibly encode, the incoming information so as to make it suitable for transmission and subsequent reception. Eventually, in a transmitter, the information modulates the carrier, i.e., is superimposed on a high-frequency sine wave. The actual method of modulation varies from one system to another. Modulation may be high level or low level, (in VHF we use low level modulation) and the system itself may be amplitude modulation, frequency modulation, pulse modulation or any variation or combination of these, depending on the requirements.

CRYSTALOSC & AMPMODULATOR& DRIVER PARF OUTPUTPOWER AMPAUDIOAMPLIFIERAUDIO IN FIG5: Block diagram of typical radio transmitter

Channel

The acoustic channel (i.e., shouting!) is not used for long-distance communications and neither was the visual channel until the advent of the laser. "Communications," in this context, will be restricted to radio, wire and fiber optic channels. Also, it should be noted that the term channel is often used to refer to the frequency range allocated to a particular service or transmission, such as a television channel (the allowable carrier bandwidth with modulation). It is inevitable that the signal will deteriorate during the process of transmission and reception as a result of some distortion in the system, or because of the introduction of noise, which is unwanted energy, usually of random character, present in a transmission system, due to a variety of causes.

Since noise will be received together with the signal, it places a limitation on the transmission system as a whole. When noise is severe, it may mask a given signal so much that the signal becomes unintelligible and therefore useless. Noise may interfere with signal at any point in a communications system, but it will have its greatest effect when the signal is weakest. This means that noise in the channel or at the input to the receiver is the most noticeable.

Receiver

There are a great variety of receivers in communications systems, since the exact form of a particular receiver is influenced by a great many requirements. Among the more important requirements are the modulation system used, the operating frequency and its range and the type of display required, which in turn depends on the destination of the intelligence received. Most receivers do conform broadly to the super heterodyne type, as does the simple receiver whose block diagram is shown in Figure.

IntermediateFrequencyAmplifierDemodulatorAudio VoltageAnd PowerAmplifiersRF StageLocalOscillatorMixerSpeakerFIG 6: Block diagram of AM super heterodyne receiver

Receivers run the whole range of complexity from a very simple crystal receiver, with headphones, to a far more complex radar receiver, with its involved antenna arrangements and visual display system. Whatever the receiver, its most important function is demodulation (and sometimes also decoding). Both these processes are the reverse of the corresponding transmitter modulation processes.

As stated initially, the purpose of a receiver and the form of its output influence its construction as much as the type of modulation system used. The output of a receiver may be fed to a loudspeaker, video display unit, teletypewriter, various radar displays, television picture tube, pen recorder or computer: In each instance different arrangements must be made, each affecting the receiver design. Note that the transmitter and receiver must be in agreement with the modulation and coding methods used (and also timing or synchronization in some systems).

Frequency band and its uses in communicationsTable 2: Radio Waves Classification

Band NameFrequency Band

Ultra Low Frequency (ULF)3Hz - 30 Hz

Very Low Frequency (VLF)3 kHz - 30 kHz

Low Frequency (LF)30 kHz - 300 kHz

Medium Frequency (MF)300 kHz - 3 MHz

High Frequency (HF)3 MHz - 30 MHz

Very High Frequency (VHF)30 MHz - 300 MHz

Ultra High Frequency (UHF)300 MHz -3 GHz

Super High Frequency (SHF)3 GHz - 30 GHz

Extra High Frequency (EHF)30 GHz - 300 GHz

Infrared Frequency3 THz- 30 THz

Table 3: Frequencies band uses in communication

36

4

NAME OF THEEQUIPMENTFREQUENCYBAND USES

NDB

HF

Localizer

VOR

VHFGlide path

DME

UHF LINKRADAR200 450 KHz

3 30 MHz

108-112MHz

108-117.975MHz

117.975-137MHz328-336MHz

960-1215MHz

.3-2.7GHz.3-12GHzLocator, Homing & En-routeGround to Ground/Air Com.Instrument Landing SystemTerminal, Homing & En-routeGround to Air Comm.Instrument Landing SystemMeasurement of DistanceRemote Control, MonitoringSurveillance

The electromagnetic spectrum

MODULATION

CW and Pulse modulation

According to the type of carrier it is possible to identify two basic types of modulation:

Continuous wave (CW) modulation- the carrier is sinusoidal.Pulse modulation- the carrier is a periodic train of pulses.

The CW modulation, being a continuous process, is obviously suitable for signals which vary continuously with time. Pulse modulation is a discontinuous process, in the sense that pulses are present at certain distinct intervals of time only making this process more suitable to messages that are discrete in nature. Continuously varying signals can be transmitted on pulsed carrier by the method of sampling.

Analog and Digital Modulation

In an alternative way modulation can be classified as Analog or Digital (or coded) modulation. This way of classification becomes more relevant and meaningful for the complex system using CW and Pulsed techniques where the distinction on the basis of the type of carrier loses its sanctity. In analog modulation the modulated parameter varies in direct proportion to the modulating signal (instantaneous value). In digital modulation, a digital transformation takes place whereby the message is converted from one symbolic language to another. If the message is originally a continuous time function, it must be sampled and digitized prior to encoding.

Types of CW Modulation

The Continuous Wave auxiliary signal (carrier), because the Message is the main signal, can be characterized by the following three parameters.

1. The Amplitude: It is the maximum instantaneous magnitude.2. The Frequency: It is the number of oscillations per second.3. The Phase: It designates the point of the oscillatory cycle reached at a specified reference time.

Amplitude Modulation

Here in VHF Airport Authority of India uses amplitude modulation for sending signals.Basic theory of AMMessage and information: We can define communication as the process of transferring information (or Message) from one point in space and time, called the source, to another point, the destination or user. A communication system is the totality of mechanism that provides the information link between source and destination. Information normally means knowledge or meaning. Information is the well organized collection of data which conveys some meaning. Within the limited scope of discussion, we are to restrict ourselves within the physical manifestation of the information as produced by the source, that is, message. Normally the message produced by a source is not electrical and hence an input transducer is required to convert the message to a signal a time varying electrical quantity such as voltage or current. Similarly, another transducer at the destination converts the output signal to the appropriate message form. In many of the books signal and message are used interchangeably since the signal, like the message, is also a physical embodiment of information.

Amplitude Modulation and Carrier: Remembering again that modulation is the systematic alteration of one waveform according to the characteristics of the message waveform we are to be ready for some quantitative discussion and analysis of modulation system. Let us start the discussion by taking an electrical signal x(t) representing time varying voltage or current. If this signal is used to alter the amplitude of a sinusoid cos {ct +(t)}

MARATHON Digital Voice Recorder (DVR)

Marathon Digital recorders are available in three models. They are as follows:a) Marathon Pro capable of handling up to 128 Analog inputs in increments of 4 and up to 120 Digital inputs.b) Marathon Advanced capable of handling up to 64 Analog inputsc) Marathon compact capable of handling up to 32 Analog inputs.Marathon Digital Recorders are based on a Standard PC Architecture and are designed as Standalone Systems, with all System Controls integrated on to the Front Panel. The System consists of all necessary Hardware Components for Recording and Storage of Voice Calls and Fax Messages. The system is also capable of simultaneous Replay during Online Recording or replay at a later time. The Marathon System is based on Pentium Pro Processor and is having a Dual Bus Architecture with both ISA and PCI slots for interface of system modules into the motherboard or Backplane. An LCD type color display of 320x240 pixel resolution is integrated into the System Front Panel for display of all related information required for operation and supervision of the System. The Marathon System is provided with data backup facilities by using Digital Audio Tape (DAT) device. All System Recordings are done in parallel mode i.e. both in the Hard disk and in any one of the Recording Devices such as DAT medium. The System is Password protected and has facilities for individual Personal Access. The Marathon System is controlled by a Front Panel IBM PC Key board compatible Control Panel. Also the System functions can be accessed and supervised through an optional PC connected to the System and is known as Marathon Workstation. For controlling the system with an external PC, the PC should be loaded with Marathon Workstation Software.

SECURITY EQUIPMENTS

DETECTION OF X-RAYSDETECTION METHOD X-rays are detected by scintillator crystals which convert X-rays into visible light, photodiodes then convert this light into electrical current. In multi energy system the single energy X-Ray beam is converted into dual energy by the following arrangement of detectors. Fig 8: conversion of X-ray to dual energy yAfter the X-rays pass through the item, they are picked up by a detector. This detector then passes the X-rays on to a filter, which blocks out the lower-energy X-rays. The remaining high-energyX-rays hit a second detector. A computer circuit compares the pick-ups of the two detectors to better represent low-energy objects, such as most organic materials.

Conveyer system and luggage detectionConveyer systemX-B is use a conveyer motor, which drives the conveyer belt to transport the luggage or baggage into the inspection tunnel. This may be a single or three phase motor depending upon the size of the machine. The conveyer motor must run at a uniform speed, single motor is used for running the conveyer belt in forward and the reverse direction by suitable phase shifting arrangement. The material of the conveyer belt is transparent to the X-Rays.

Luggage detectionLight barriersThe light barriers serve to detect objects transported on the conveyor belt into the inspection tunnel. As standard, a light barrier is installed at the tunnel entry so that inspections can only be carried out in forward direction. X-ray units equipped with the option Full-reverse mode provide another light barrier at the tunnel exit. In this case, inspections can be carried out in both forward and reverse direction.The light barriers operate with infrared beams. If an object interrupts a beam, the output signal of the light barrier changes its state (logic level) and the object is detected. A number of light barriers may be required at suitable locations so as to detect objects of various shape and sizes.

METAL DETECTORS

INTRODUCTION TO AIRPORT METAL DETECTORSOld metal detectors worked on energy absorption principle used two coils as search coils; these were forming two loops of a blocking oscillator. When any person carrying a metallic object or a weapon stepped through the door carrying coils, some energy was absorbed and the equilibrium of the blocking oscillator got disrupted. This change was converted into audio and visual indications. Size and weight of the metallic object was determined by proper sensitivity settings. The hand held metal detectors used the same technique. These types of metal detectors carried various shortcomings and they have been superseded by new generation multi zone equipmentsWorking on PI technology TYPES- The metal detectors, used in aviation sector are generally of two types.1. HAND HELD METAL DETECTORS2. DOOR FRAME METAL DETECTORS Hand Held Metal DetectorOPERATIONThe coil is part of the oscillating circuit which operation frequency is 23.5 kHz.When a metal object is inside the sensing area of the coil, it will effect to amplitude of the oscillating signal. After a while the integrating control will set the amplitude a constant value. Output of oscillator is rectified and it is connected through the filter section to comparator. When the signal is lower than the adjusted reference level (sensitivity setting) comparator generates alarm signal. It activates the alarm oscillator and the audible alarm / the red alarm light. Battery voltage is controlled with a low voltage circuit and constant alarm is activated when the battery voltage is under 7V. The connector in the rear of the unit operates as headphone and charger connections. The charger idle voltage is between 14 and 24 VDC. During charging operation the green light is plinking and with full battery it lights constantly. If headphone is connected, audible alarm is not operational.

DOOR FRAME METAL DETECTOR

FIGURE13: View of a Door Frame (WALK THROUGH) Metal Detector

Technical Description FUNCTIONMetor 200 metal detector is designed to activate an alarm when the signal caused by a metal object taken through the detector exceeds the preset alarm level. Due to the multizone principle used in Metor 200 it discriminates reliably weapons from innocuous item and indicates the height where a weapon was taken through the gate.PRINCIPLE OF OPERATIONThe transmitter coils generate a pulsed magnetic field around them. Metal objects taken through the detector generate a secondary magnetic field, which is converted into a voltage level by the receiver coils. Metor 200 consists of eight separate overlapping transmitter and receiver coil pairs. The signals received from each receiver coil are processed individually thus the transmitter and receiver coil pairs form eight individual metal detectors. The operation is based on electromagnetic pulsed field technology as below in addition to theAbove explanation

BIBLIOGRAPHY

The information mentioned above is taken from the following sources:

http://www.wikipedia.org

http://www.aai.aero

http://www.airport-technology.com

http://www.navfltsm.addr.com/gs.htm

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