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IT Literacy

IT Literacy   Literacy is being able to read, write, listen, speak, view and represent while thinking critically and creatively about ideas and information. Literacy enables us 10 understand ourselves and the world around us, to interact with others and to share thinking. Now days, IT Literacy programmed are initiated by the Central Govt. and State Govt. and made it compulsory to create IT skilled professionals in their recruitment policies. IT literacy is also known as computer Literacy.   Computer Literacy Computer literacy is the ability to use computers and related technology efficiently, with a range of skills covering levels from elementary use to programming and advanced problem solving. By another measure, computer literacy requires some understanding of computer programming and how computers work.   10 things we have to know to be computer literate:  
  • Search Engines
    • Using a search engine is more than typing in the address, putting a couple of keywords into the big text box, clicking Search, and choosing the first result. While that may work, it won't give you the best results much of the time. Learning the advanced search, Boolean operators, and how to discern good results from bad results goes a long way toward enabling you to use a computer as a powerful research tool.  
  • Word processing
    • Word processing is one of the oldest uses for a computer. And it continues to be extremely important, even though in many ways its functions have been put into other applications. (For example, people may write more emails than documents, but the task is nearly identical.) It is tough to claim to be computer literate if the basic functions of word processing - like spell check, table creation, and working with headers - are outside your capabilities.  
  • Spreadsheets.
    • A spreadsheet is an interactive computer application for organization, analysis and storage of data in tabular form. Spreadsheets are developed as computerized simulations of paper accounting worksheets. The program operates on data entered in cells of a table. Each cell may contain either numeric or text data, or the results of formulas that automatically calculate and display a value based on the contents of other cells. A spreadsheet may also refer to one such electronic document.  
  • Browser basics
    • Mastering techniques like opening links in new window using bookmarks, editing URLs to perform navigation clearing the browser cache, and understanding common error messages will give us access to a world of unlimited information instead of keeping we stuck with only what web site designers make obvious.  
  • Virus/malware scanning
    •   Much of typical computer maintenance is automated unneeded at that point, but it is still essential to understand how to check a system for nasty bugs, spyware, and other malicious applications. While the scanning tools come with real-time monitors, something can still slip onto the system before the scanner has the right filter for it. So it's critical know how to trigger a manual virus/malware scan, as more...
    Catgeory: Railways

    Electric Circuits and Field

    Electric Circuits and Field   BASIC CONCEPTS An electric circuit is a path in which electrons from a voltage or current source flow. The point where those electrons enter an electrical circuit is called the "source" of electrons. The point where the electrons leave an electrical circuit is called the "return" or "earth ground". The exit point is called the "return" because electrons always end up at the source when they complete the path of an electrical circuit. The part of an electrical circuit that is between the electrons' starting point and the point where they return to the source is called an electrical circuit's "load". The load of an electrical circuit may be as simple as those that power home appliances like refrigerators, televisions, or lamps or more complicated, such as the load on the output of a hydroelectic power generating station. At the heart of these electrical devices are made by assembly of electrical components. These component are classified in two categories i.e., active components and passive components. are components are: semiconductors, transistors, diodes and triodes, current source, voltage source. However, these devices could not function without much simpler components known as passive component these include resistors, capacitors and Inductors   RESONANCE Resonance in electrical circuits consisting of passive and active elements represents a particular state of the circuit when the current or voltage in the circuit is maximum or minimum with respect to the magnitude of excitation at a particular frequency, the circuit impedance being either minimum or maximum at the power factor unity.   Series Resonance     Resonance Properties of Series RLC Circuit  
  • The applied voltage and the resulting current are in phase which also mean that the p. f. of the RLC series resonant circuit is unity.
  • The net reactance is zero at resonance and impedance does have the resistive part only.
  • The current in the circuit is maximum and is (V/R) A.
  • At resonance, the circuit has got minimum impedance and maximum admittance.
  • Frequency of resonance is given by \[{{f}_{0}}=\frac{1}{2\pi \sqrt{LC}}Hz\]
  • Q factor of series resonant circuit is given by
    • \[Q=\frac{1}{{{\omega }_{0}}RC}=\frac{1}{\frac{1}{\sqrt{LC}}RC}=\frac{1}{R}\sqrt{\frac{L}{C}}.\] \[Also,\,\,Q\,=\frac{{{f}_{0}}}{Bandwidth}=\frac{\operatorname{Re}sonant\,\,frequency}{Bandwidth}\]   Parallel Resonant     Properties of Parallel Resonant LRC Circuit  
  • Power factor is unity
  • Current at resonance is [V/ (L/CR)] and is in phase with the applied voltage. The value of current at resonance is minimum.
  • Net impedance at the resonance of parallel circuit is maximum and equal to (L/CR)\[\Omega \]
  • The admittance is minimum and net susceptance is zero at resonance.
  • The resonant frequency of this circuit is given by- \[{{f}_{0}}=\frac{1}{2\pi }\sqrt{\frac{1}{LC}-\frac{{{R}^{2}}}{{{L}^{2}}}}\]
    •   Resonance Between Parallel RC and RL Circuit   Let        \[{{Y}_{1}}\]= admittance of \[{{R}_{1}}C\]circuit \[{{Y}_{2}}\]= admittance of\[{{R}_{2}}L\] circuit Y= net admittance \[={{Y}_{1}}+{{Y}_{2}}\]             \[=\left[ \frac{{{R}_{1}}}{R_{1}^{2}+X_{C}^{2}}+\frac{{{R}_{2}}}{R_{2}^{2}+X_{L}^{2}} \right]+j\,\,\left[ \frac{{{X}_{C}}}{R_{1}^{2}+X_{C}^{2}}-\frac{{{X}_{L}}}{R_{2}^{2}+X_{L}^{2}} \right]\] Important Point  
    • Circuit will be resonant for any frequency provided
    \[{{R}_{1}}={{R}_{2}}=\sqrt{L/C}\]
    • Resonant frequency,
    more...
    Catgeory: Railways

    Electrical Machine

    Electrical Machine   SINGLE PHASE TRANSFORMER
    • A transformer is a static device through which electrical power from one circuit is transferred to the other circuit at the same frequency.
    • It can raise or lower the voltage in a circuit with a corresponding decrease or increase in the current.
      EMF Equation of a Transformer \[{{E}_{1}}=4.44f{{\phi }_{m}}{{N}_{1}},\] where,\[{{E}_{1}}\]= RMS value of induced emf in primary winding f= frequency \[{{\phi }_{m}}\]= maximum flux in core \[{{N}_{1}}\]= number of turns in primary winding. Similarly, \[{{E}_{2}}=4.44f{{\phi }_{m}}{{N}_{2}},\] where,\[{{E}_{2}}\]= RMS value of induced emf in secondary winding \[{{N}_{2}}\]= Number of turns in secondary winding Thus,           \[\frac{{{E}_{2}}}{{{E}_{1}}}=\frac{{{N}_{2}}}{{{N}_{1}}}=\frac{{{V}_{2}}}{{{V}_{1}}}=\frac{{{I}_{1}}}{{{I}_{2}}}=K\]   Losses in Transformer
  • Core loss or Iron loss
    • It includes both hysteresis and eddy current loss.
    • The core losses are almost constant at all loads.
  • Copper loss
    • This loss is due to the ohmic resistance of the transformer winding and hence this loss depends on the value of current.
    • This loss is different at different loads.
      Equivalent Circuit Equivalent Circuit of transformer is showing in fig. Let \[{{I}_{1}}\]\[=\]primary current \[{{R}_{1}}\]\[=\]primary resistance \[{{X}_{1}}\]\[=\]primary leakage reactance \[{{I}_{0}}\]\[=\]no load current \[{{I}_{2}}\]\[=\]secondary current transferred to primary \[{{I}_{W}}\]\[=\]watt full component of no load current \[{{I}_{\mu }}\]\[=\]magnetizing component of no load current \[{{R}_{0}}\]\[=\]core loss resistance \[{{X}_{0}}\]\[=\]magnetizing reactance \[{{E}_{1}}\]\[=\]RMS value of induced emf in primary winding \[{{E}_{2}}\]\[=\]RMS value of induced emf in secondary winding \[{{R}_{1}}\]\[=\]secondary resistance \[{{X}_{2}}\]\[=\]secondary leakage reactance     Phaser diagram From the equivalent circuit of transformer, it can concluded that \[{{E}_{2}}={{V}_{2}}+{{I}_{2}}{{R}_{2}}+{{I}_{2}}{{X}_{2}}\] \[{{I}_{1}}={{I}_{0}}+{{I}_{2}}'\] \[{{I}_{0}}={{I}_{W}}+{{I}_{\mu }}\] \[{{V}_{1}}={{E}_{1}}+{{I}_{1}}{{R}_{1}}+{{I}_{1}}{{X}_{1}}\] Phaser diagram is showing in fig.     Fig. Phaser diagram   THREE PHASE TRANSFORMER A three phase transformer or\[3-\phi \]transformer can be constructed either by connecting together three single-phase transformers, thereby forming a so-called three phase transformer bank or b) using one pre-assembled and balanced three phase transformers which consists of three pairs of single phase windings mounted onto one single laminated core. In the case of three phase transformer windings, three forms of connection are possible: "star" (wye), "delta" (mesh) and "interconnected-star" (zig-zag). The combinations of the three windings may be with the primary delta-connected and the secondary star-connected, or star-delta, star-star or delta-delta, depending on the transformers use as shown in fig. When transformers are used to provide three or more phases they are generally referred to as a Polyphase Transformer.
    Primary configuration Secondary configuration
    Delta (mesh)       more...
    Catgeory: Railways

    Power System

    Power System   BASIC POWER GENERATIONS CONCEPT Energy exists in various forms like mechanical energy, electrical energy, thermal energy and so on. One form of energy can be converted into another form by suitable arrangements. Out of these forms, electrical energy is preferred due to the following reasons.
    • It can be easily transported from one form to another
    • Losses in energy transportation are minimum
    • It can be easily controlled and regulated to suit requirements
    • It can be easily converted into other forms of energy particularly mechanical and thermal
    • It can be easily sub-divided.
    In all power stations, electric energy is generated from other forms of energy e.g.
    • Chemical energy of fuel (thermal energy)
    • Energy of falling water (hydraulic energy)
    • Atomic energy (nuclear energy).
    Accordingly power stations are classified as:   (A) Thermal Power Stations Those power stations which convert chemical energy of fuel (coal, diesel etc.) into electrical energy are called thermal power stations. The fuel used in thermal power stations maybe solid fuel (coal) or liquid fuel (diesel). The chemical energy of fuel is used to run the prime mover to which is coupled the alternator (A.C. generator). Thus electrical energy is obtained from the alternator. According to the prime-mover employed for driving the alternate, thermal power stations may be broadly divided into the following two important types: (a) Steam power stations: Steam power stations employing steam engine or turbine as the prime-mover. Coal is used fuel. (b) Diesel power stations: Diesel power stations employing diesel engine as the prime-mover.     (B) Hydro-electric Power Stations These convert energy of falling water (hydraulic) into Electrical energy The entire arrangements can be divided into the following stages for the sake of simplicity:
  • Water reservoir. 2 Dam.
  • Valve house. 4. Penstock.
  • Water turbine. 6. Alternator.
    •   (C) Nuclear Power Stations These convert nuclear energy into electrical energy. Nuclear power reactor: Nuclear power reactor is basically that part of nuclear power plant where energy released as a result of nuclear fission of radioactive material is utilized to heat the coolant which may in turn generate steam or be used in a gas turbine. The nuclear reactor may thus be regarded as a substitute for the boiler fire box of steam plant or combustion chamber or a gas turbine plane. The steam or the gas may be used as working fluid in nuclear power plant. The nuclear power plant maybe of steam driven turbine or gas driven turbine as per the choice of the fluid.     The following Junctions are associated with the working of nuclear reactor: (i) Producing a chain reacting or critical system, (ii) Controlling the level of power release from the system, (iii) Using spare neutrons to convert fertile into fissile material, (iv)Protecting personnel from harmful radiations emanating from the core.   TRANSMISSION At the more...
    Catgeory: Railways

    Control System

    Control System   CONTROL SYSTEM It is an arrangement of different physical components in such a way that we get the desired output from the input.   Classification of Control System
    • Open Loop Control System: It is a system which has no feedback & its output has no effect on control action, as shown in fig.
        For example: traffic light, tap of water etc. Advantages: These systems are simple in construction & design; economic in nature; easy from the maintenance point of view, have high stability & are convenient to use when the output is difficult to measure. Disadvantages: These systems are not accurate & reliable as the accuracy depends on the calibration of the inputs & their operation is affected due to the presence of non-linearities in the elements.
    • Closed Loop System: It is a system which takes feedback & its output has an effect on the control action through that feedback, as shown in fig.
    For example A. C., humans etc. Advantages: These systems have high accuracy: system errors can be modified as these systems can sense environmental changes as well as internal disturbances. They also have less reduced effects of non-linearities, and have high bandwidth Disadvantages: These systems are complicated to construct, and are costly & unstable in nature.   PRINCIPLE OF FEEDBACK In the open loop system, there is no feedback path, but this feedback path exists in a closed loop system. So, in a closed loop system, the output will also depend on the feedback system. The purpose of feedback is to reduce the error which exists due to the difference in reference input and system output. There are two types of feedback: 1)   Positive feedback 2)   Negative feedback Positive feedback: When the output which is fed as an input to the system, is in the same phase with the input, then this feedback increases the input or it is added to the input. The positive feedback is used in oscillator circuits. For positive feedback, error signal \[=r(t)+c(t)\]     Negative feedback: When the output which is fed as an input to the system, is in a completely opposite phase to the input, then this feedback reduces the input or is subtracted from the input. This feedback helps in stabilizing the gain of the amplifier. Negative feedback is used in amplifier circuits. For negative feedback, error signal =r (t) - c (t)     Effects of Feedback:
    • Gain is reduced by a factor & there is reduction of parameter variation by a factor of {1 + G(s) H(s)}.
    • There is improvement in sensitivity & a reduction in stability, i.e. the system might become unstable.
    • Feedback can reduce the effects of noise & disturbance on the system's performance; there by making more...
    Catgeory: Railways

    Electrical Measurement and Instrumentation

    Electrical Measurement and Instrumentation   The measurement methods can be analog or digital methods, deflection or null methods, active or passive methods, direct or indirect methods and absolute or secondary methods. Measurement generally involves an instruments as a physical means of determining an unknown quantity or a variable called the parameter. The instrument is a means for determining the value or magnitude of the measured. The instruments can also be divided into separate classes according to several criteria as, analog or digital instrument, deflection or null type instruments, power operated (active) or self generating (passive) instruments, contacting or non contacting instruments, mechanical or electrical instruments and  or control instruments.   CLASSIFICATION OF INSTRUMENTS   Permanent Magnet Moving Coil Instrument
    • PMMC instruments are used only to measure DC quantities and not AC quantities. This is because permanent magnets are used for creating magnetic fields.
    • Torque equation
    Deflecting torque, \[{{T}_{d}}\propto I\] And controlling torque, \[{{T}_{c}}={{K}_{c}}\theta \] At steady position of pointer, \[{{T}_{c}}={{T}_{d}}\] And thus, \[I\propto \theta \] - since the deflection is directly proportional to the current flowing through the instrument, we get a uniform scale for the instrument. - D.C. voltage and D.C. current can be measured using PMMC instruments.   Moving Iron Type Instrument In movingiron instruments the movable system consists of one or more pieces of specially-shaped soft iron, which are so pivoted as to be acted upon by the magnetic field produced by the current in coil. There are two general types of moving-iron instruments namely. (i) Attraction type (ii) Repulsion type.   Attraction Type
    • Due to the magnetic field, the moving iron is attracted towards it and due to this force of attraction, the pointer deflects. This deflection of pointer is controlled by the controlling forces and thus, the pointer comes to rest and we get a reading on the scale.
    • Torque equation
    Deflecting torque, \[{{T}_{d}}=K{{I}^{2}}\] And controlling torque,  \[{{T}_{c}}={{K}_{1}}\sin \theta \] At steady position of pointer, \[{{T}_{c}}={{T}_{d}}\] And thus, \[\theta \propto {{I}^{2}}\]
    • Since deflection of the pointer is directly proportional to the square of the current, the scale of the attraction type moving iron type instrument is not uniform.
      Repulsion Type In repulsion type instrument, two vanes of soft iron are used inside the coil. One vane is fixed and the other one is free to move. When current flows through the coil, both vanes are magnetized and therefore, there is a force of repulsion between the two and this force acts as the driving force for the instrument. Two different designs of repulsion type moving iron type instruments are common - radial type and co-axial type.   Electro Dynamometer Type Instrument
    • This type of instrument is capable of measuring AC voltage and AC current as well as DC voltage and DC current.
      Induction Type Instruments
    • Induction type instrument works on the principle of induction and therefore, this method is used in measuring
    • AC voltage and AC current.
      MEASUREMENT more...
    Catgeory: Railways

    Utlization of Electrical Energy

    Utlization of Electrical Energy   In electrical engineering, utilization factor, is the ratio of the maximum load which could be drawn to the rated capacity of the system, this is closely related to the concept of Load factor The Load factor is the ratio of the load that a piece of equipment actually draws (time averaged) when it is in operation to the load it could draw (which we call full load).   ELECTRICAL DRIVE Electrical drive system is widely used in large number of industrial and domestic applications like factories, transportation systems, textile mills, fans, pumps, motors, robots etc. The main advantage of this concept is, the motion control is easily optimized with the help of drive. In very simple words, the systems which control the motion of the electrical machines, are known as electrical drives. A typical drive system is assembled with a electric motor and a sophisticated control system that controls the rotation of the motor shaft. Now days, this control can be done easily with the help of software. So, the controlling becomes more and more accurate and this concept of drive also provides the ease of use. Drives are employed as prime movers for diesel or petrol engines, gas or steam turbines, hydraulic motors and electric motors. The very basic block diagram an electric drives is shown below. The load in the figure represents various types of equipment’s which consist of electric motor, like fans, pumps, washing machines etc     CLASSIFICATION OF ELECTRIC DRIVES The classification of electrical drives can be done depending upon the various components of the drive system. Now according to the design, the drives can be classified into three types such as single-motor drive group motor drive and multi motor drive. The single motor types are the very basic type of drive which are mainly used in simple metal working, house hold appliances etc Group electric drives are used in modem industries because of various complexities. Multi motor drives are used in heavy industries or where multiple motoring units are required such as railway transport. If we divide from another point of view, these drives are of two types:                                  
  • Reversible types drives
  • Non reversible types drives.
    • One classification point of view is how many motors (axis are operated from one device. There are one and multiple (axles) are operated electronic drives.                                        Electrical Drive System:    The main components of an electrical drive system can be seen in Figure below.                                        The thick arrows denoting the way of energy flow. Depending on the actual application there may be a two-way energy flow the load side.                                        Electromagnetic motors are also capable of the two-way energy flow, but for the power electronic devices this is not always possible especially for the older types.                             ELECTRICAL MOTOR  The electrical motor is a device that has brought about one the more...
    Catgeory: Railways

    Basic Electronics

    Basic Electronics   Electronics is considered to be a branch of Physics and Electrical engineering, Electronics is the science of controlling electrical energy electrically, in which the electrons have a fundamental role. Electronics deals with electrical circuits that involve active Electrical components such as vacuum tubes, transistors, diodes, migrated circuits, associated passive electrical components, and interconnection technologies. Commonly, electronic devices contain circuitry consisting primarily or exclusively of active semiconductors supplemented with passive elements; such a circuit is described as an electronic circuit.   Industrial Electronics Insustrial electronics is a branch of electronics that deals with power electronic devices such as thyristors, SCRs, AC/DC drives, meters, sensors, analyzers, load cells automatic test equipment, multi-meters, data recorders, relays, resistors, semiconductors, transistors, waveguides, scopes, amplifiers, radio frequency (RF) circuit boards, timers, counters, etc. It covers all of the methods And facets of: control systems, instrumentation, mechanism and diagnosis, signal processing and automation of various industrial applications. The core research areas of industrial electronics include electrical power machine designs, power conditioning and power semiconductor devices, A lot of consideration is given to power economy and energy management in consumer electronic products. The scope of industrial electronics ranges from the design and maintenance of simple electrical fuses to complicated programmable logic controllers (PLCs), solid-state devices and drives. Industrial electronics can handle the automation of all types of modem day electrical and mechanical industrial processes, Some of the specialty equipment used in industrial electronics includes: variable frequency converter and inverter drives, human machine interfaces, hydraulic, positioners and computer or microprocessor controlled robotics. Electronic Components and Their Functions
  • Semiconductors: Electronic control components with no moving parts.
  • Transistors: A semiconductor device capable of amplification.
  • Resistors: Components used to resist current.
  • Switches: Components that may be made to either conduct (closed) or not (open).
  • Capacitors: Components that store electrical charge in an electrical field.
  • Terminals and Connectors: Components to make electrical connection.
  • Magnetic or Inductive Components: These are Electrical components that use magnetism.
  • Network Components: Components that use more than type of Passive Component.
  • Piezoelectric devices, crystals, resonators: Passive components that use piezoelectric effect.
  • Diodes: Components that conduct electricity in only one direction.
  • Integrated Circuits or ICs: A microelectronic computer electronic circuit incorporated into a chip or semiconductor; a whole system rather than a single component.
    •   Electronic tube or Vacuum tube Vacuum tube is a device that controls electric current between electrodes in an evacuated container. The concept of thermionic valve or vacuum tubes used the idea that a heated element in a vacuum emitted electrons that would normally remain in the vicinity of this heated element because of the charge attraction. If a second electrode was placed into the vacuum and a high positive potential placed on it, then the electrons would be attracted away from the heated element towards this element with a high potential. As a result a current would flow in this direction. As electrons were unable to travel in the reverse direction, this simple valve or vacuum more...
    Catgeory: Railways

    Communication System

    Communication System   MODULATION The process of impressing low-frequency information to be transmitted on to a high-frequency wave, called the carrier wave, by changing the characteristics of either its amplitude, frequency, or phase angle is called modulation. The main function of the carrier wave is to carry the audio or video signal from the transmitter to the receiver. The wave that is resulted due to superimposition of audio signal and carrier wave is called the modulated wave.   Types of Modulation   AMPLITUDE MODULATION (AM) The method of varying amplitude of a high frequency carrier wave in accordance with the information to be transmitted, keeping the frequency and phase of the carrier wave unchanged is called Amplitude Modulation. The information is considered as the modulating signal and it is superimposed on the carrier wave by applying both of them to the modulator. The detailed diagram showing the amplitude modulation process is given below.     Modulation Index (m) The ratio between the amplitude change of carrier wave to the amplitude of the normal carrier wave is called modulation index- It is represented by the letter 'm'. It can also be defined as the range in which the amplitude of the carrier wave is varied by the modulating signal. \[m={{V}_{m}}/{{V}_{c}}\] Percentage modulation, \[%\,\,m={{m}^{*}}100={{V}_{m}}/{{V}_{c}}*100\] The percentage modulation lies between 0 and 80%.   Power Relations in an AM wave   A modulated wave has more power than had by the carrier wave before modulating. The total power components in amplitude modulation can be written as: \[{{P}_{total}}={{P}_{carrier}}+{{P}_{LSB}}+{{P}_{USB}}\] Considering additional resistance like antenna resistance R. \[{{P}_{carrier}}={{[({{V}_{c}}/\sqrt{2})/R]}^{2}}={{V}^{2}}_{C}/2R\]   ANGLE MODULATION In the angle modulation, again there are two different types of modulations. Frequency modulation. Phase modulation.  
  • Frequency Modulation
    • To generate a frequency modulated signal, the frequency of the radio carrier is changed in line with the amplitude of the incoming audio signal. When the audio signal is modulated onto the radio frequency carrier, the new radio frequency signal moves up and down in frequency. The amount by which the signal moves up and down is important. It is known as the deviation and is normally quoted as the number of kilo hertz deviation. As an example the signal may have a deviation of plus and minus 3 kHz, i.e. \[\pm \,\,3\,\,kHz.\]In this case the carrier is made to move up and down by 3 kHz. Broadcast stations in the VHF portion of the frequency spectrum between 88.5 and 108 MHz use large values of deviation. typically \[\pm \,\,75\,\,kHz.\] This is known as wide-band FM (WBFM). These signals are capable of supporting high quality transmissions, but occupy a large amount of bandwidth. Usually 200 kHz is allowed for each wide-band FM transmission. For communications purposes less bandwidth is used. Narrow band FM (NBFM) often uses deviation figures of around \[\pm \,\,3\,\,kHz.\]It is narrow band FM that is typically used for two-way radio communication applications. more...
    Catgeory: Railways

    Radio Communication and Radar Systems

    Radio Communication and Radar   Systems   ROBOTIC RADIO COMMUNICATIONS SYSTEMS The System "Wireless Technology or Radio Based Robot Communication System" is developed for the purpose of achieving tasks that are almost impossible for the humans and for using them in hazard prone areas. The system consists of a master robot slave robot, voice module and the communication takes place with the help of a voice module. The signal is transmitted and received by the zigbee networks installed on every wireless module. The commands are given only to the master robot using the voice module and this is transmitted to the master robot via zigbee. The master robot performs the actions commanded to it, transfers the same commands to the slave robot(s) and hence performs the same actions as the master robot does. Here the zigbee in voice module acts as a transmitter, in master robot both a transmitter as well as a receiver and only as a receiver in the slave robot. Zigbee Technology Zigbee is the name of a specification that suites high level communication protocols using small, low-power digital radios based on the IEEE 802.15.4 standard for wireless personal area networks (WPANs), such as wireless headphones connecting cell phones via short-range radio. The technology is intended to be simpler and cheaper than other WPANs, such as Bluetooth. Zigbee is targeted at radio frequency (RF) applications which require a low data rate, long battery life, and secure networking.                   . Zigbee Module Zigbee is a wireless technology developed as an open global standard to address the unique needs of low-cost, low-power wireless M2M networks. The Zigbee standard operates on the IEEE 802.15.4 physical radio specification and operates in unlicensed bands including 2.4 GHz, 900 MHz and 868 MHz Zigbee builds upon the physical layer and medium access control defined In IEEE standard 802, 15.4 (2003 version) for low-rate WPAN's. The specification goes on to complete the standard by adding four main components: network layer, application layer, Zigbee device objects (ZDO's) and manufacturer-defined application objects which allow for customization and favor total integration.   Radio waves Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared-light. Radio waves have frequencies as high as 300 GHz to as low as 3 kHz, though some definitions describe waves above 1 or 3 GHz as microwaves, or include waves of any lower frequency. At 300 GHz, the corresponding wavelength is 1 mm (0.039 in), and at 3 kHz is 100 km (62 mi). Like all other electromagnetic waves, they travel at the speed of light. Naturally occurring radio waves are generated by lightning, or by astronomical objects. The basic building block of radio communications is a radio wave. Like waves on a pond, a radio wave is a series of repeating peaks and valleys. The entire pattern of a wave, before it repeats itself, is called a cycle. The wavelength is the distance a more...
    Catgeory: Railways

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