ĐIỆN tử VIỄN THÔNG DTVT2 nhom5 bai5 khotailieu

LESSON UNIT 9: ALARM SYSTEMS Task1: The government's three-pronged attack on car crime aimes to persuade: motor manufacturers to fit alarm systems on cars car owners to be more vigilant about car thieves insurance companies to offer lower premiums for motorists who install alarm systems Task 2: The diagram shows a circuit of an alarm indoor system The diagram shows detection devices They are pressure mat, window foil, passive infra-red detector, sense circuit, key-operated switch control box, bell, door switch, power For example, when you open the door, the bell rings The control box switch is operated with a key so that the user can switch the sound of the bell or turn off/on without unplugging the power According to the diagram, the system works as a circuit of electricity works because it operates when connected but it doesn’t when disconnected 6 The problem with this circuit may be that it’s Task3 1.door switch: will the magnet mounted on moving parts of the door 2.window foil : when the foil is broken they will alarm 3.pressure mat: the pressure of someone stepping on them causes two thin metal plates inside to comes in contact Task 1) 2) 3) 4) 5) 6) 7) If a burglar disconnects the supply, the alarm continues to operate on batteries If the glass is broken, the foil breaks too If the door is opened, a magnet on the door trips a switch on the frame If a window is opened, a magnet on the moving part trips a switch If you are not there to reset the system,the alarm stops after a set time If a burglar tries to force the alarm open, tamper sensor trigger the alarm If someone steps on them, two thin metal plates come in contact Task 1) 2) 3) 4) 5) 6) 7) 8) If pressure mats constantly walked on them, two thin metal plates inside to come in contact and setting off the alarm If you fit an exit delay, an audible warning during the delay period is a useful reminder If your system does not have an automatic cut-off, the noise goes on for hour If a burglar walker in front of a motion sensor, the alarm will trigger Vibration sensor will respond if the glass is broken Tamper sensor will trigger the alarm if a burglar tries to force the box open A magnet on the moving part trips a switch if the window or door is opened The alarm stops after a set time if you are not there to reset the system Task Sensing device Used to detect LDR light thẻrmistor Heat microphone sound when light falls on LDR, its resistance decreases the sensitivity of the input can be adjusted using RV1 a large back EMF, which would destroy the transistor, could be generated across the relay Task 10 1) 2) 3) 4) The diagram shows a reed switch Because the reeds are sealed in a glass envelope to protect them Because the envelope helps to prevent corrosion of the contacts When a magnet is brought close the reeds, they are magnetized, attract each other, and close When the magnet is removed, the reeds open Task Integrated circuit (1f) circuit diagram (2j) alternating current (3g) primary cell (4b) zener diode (5e) remote control (6i) reed wave (7k) surface switch ( 8c) vibration sensor (9a) reverse bias (10 h) main supply (11d)