ĐIỆN tử VIỄN THÔNG DTVT2 nhom4 bai5 txt khotailieu

Alarm Systems D8-DTVT2 Group : Ngô Đắc Quân Lê Văn Hoạch Phùng Thế Quảng Phạm Thị Minh Phượng Nguyễn Thị Phương Ngô Thị Phượng Nguyễn Nhật Thư Nguyễn Tuấn Anh Task 1: Tuning- in Task 2: Study the diagram at the top of the following page Try to answer these questions: - What does this diagram show a circuit of? It’s a alarm system to use at home How many detection devices does it show? Name them There are seven: Bell, door switch, window fail, passive infra-red detector, pressure mat, sense circuit and key-operated switch control box What warning device does it show? It show about light and voice (bell) Why is the control box switch operated with a key? Because only one people who live in this house have a key to control the alarm syster No body can this How does the system work? When somebody touch one of this system, they will know about the bias and will have a buzz to notice What problem is there with this circuit? Use a lot of electrics Will have a buzz with a small change Task 3: Work in group Task 4: How could the system shown in Task be improved? Note your ideas Now read this text to check which of your ideas are described We can make the simple alarm circuit more effective by including some of these features Entry and exit delays! These mean you won’t set off the alarm when leaving or returning to the house On the better systems, the delays are adjustable An audible warning during the delay period is a useful reminder Automatic cut-off! This will stop the alarm after it has sounded for a set time, so that the noise doesn’t go on for hours if you’re not there to reset the system In better systems, the alarm automatically resets at the end of the alarm time Tamper protection The control panel incorporates sensors which will trigger the alarm if a burglar tries to force the box open Battery backup! This means the alarm will continue to work in a power cut, or if an intruder disconnects the mains supply Task 5: Match each action with its consequence Then identify the device or feature described 1-C, A burglar disconnects the supply The alarm continues to operate on batteries 2-E, The glass is broken The foil breaks too 3-F, A door is opened A magnet on the door trips a switch on the frame 4-D, A window is opened Two thin metal plates come in contact 5-A, You’re not there to reset the system A magnet on the moving part trips a switch 6-G, A burglar tries to force the alarm open The alarm stops after a set time 7-B, Someone steps on them Tamper sensor trigger the alarm Task 6: Complete these sentences with a suitable action or consequence 1, If pressure mats are constantly walked on, it should be regularly tested and replaced 2, If you fit an exit delay, An audible warning during the delay will be a useful reminder 3, If your system doesn’t have an automatic cut-off, the bell will ring everytime 4, If a burglar walks in front of a motion sensor, it will generate the bias, then the bell will operate to inform the change 5, Vibration sensors will respond if it find out the change of enviroment 6, Tamper sensors will trigger the alarm if a burglar tries to force the box open 7, A magnet on the moving part trips a switch if the window or door is opened 8, The alarm stops after set time if you’re not there to reset the system Task 7: Speaking practice Task 8: Word study 1-f, Integrated circuit 2-j, Circuit diagram 3-k, Alternating wave 4-d, Primary supply 5-e, Zener diode 6-i, Remote control 7-b, Reed cell 8-a, Surface sensor 9-h,Vibration bias 10-g, Reverse current 11-c, Mains switch Task 9: Technical reading Alarm systems 1, Complete this table Sensing device Use to detect LDR Light Electronic Switch Heat Output transducer Sound 2, What effect does light have on an LDR? - Its resistance decreases 3, What is the purpose of RV1 in Fig on page 53? - It will be adjusted the sensivity of the input 4, Use words from the text to complete the following table: Term Cut-off Fixed resistor Increases Opposite Saturation Change resistor Reduction Energize Slow To cause Forward bias De-energize Fast Passive Forward fixed Task 10: Explanations The diagram shows a reed switch It consists of two reeds made of ferromagnetic material They are easily magnetized and demagnetized The reeds are sealed in a glass envelope to protect them The envelope contains notrogen, which helps to prevent corrosion of the contacts When a magnet is brought close to the reeds, they are magnetized, attract each other, and close When the magnet is removed, the reeds open