DTVT2.Nhom3.Bai5 Alarm system Task 2: Alarm system There are detection devices: door switch, window foil, pressure mat, passive intra-red detector Bell Because they want nobody can control this system except the host The bell would rang if the door is opened, if glass is broken, if there is movement in the room The problem is about control box If the bad guys destroyed the control box, every devices would be counteracted Task 3: Door switch: The use magnetic switches on door A magnet mounted on the morning part of the door trips a switch mounted on the frame when the door is opened Window foil: They fit Break detectors on the inside surface of glass in windows If the glass is broken the foil breaks too Pressure mats: The fit them under the carpet at the bottom of the stairs/ the pressure of someone stopping on them causes two thin metal plates inside to come in contact, setting off the alarm Passive intra-red detector: They use passive intra-red to detect movement within their range Task 4: Task 5: C E F A G B D The alarm continues to operate on batteries if a burglar disconnects the supply If the glass is broken, the foil breaks too If a 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’re not there to reset the system, the alarm stops after a set time Tamper sensors trigger the alarm if a burglar tries to force the alarm open If someone steps on them, two thin metal plates come in contact Two thin metal plates come in contact You won’t bet off the alarm when leaving The noise goes on the for hours The motion sensor detect movement within their range The glass is broken Task 6: The burglar tries to force the alarm open The doors or windows are opened You fit are automatic cut-off Task 8: F Task 9: Sensing device LDR Thermistor Microphone Switch off and by the electronic switch Used to detect Light Heat Sound The increased current causes the relay to operate and switch on the output circuit Term Fixed resistor Increases Energize Slow To cause Forward bias Opposite Rheostat Diminished Fast Task 10: The diagram shows a reed switch Because the reeds are sealed in a glass envelope to the protect them Because it helps to prevent corrosion of the contacts When a magnet is bought close to the reeds, they are magnetized, attract each other, and close When the magnet is removed, the reeds open