ĐIỆN tử VIỄN THÔNG DTVT2 nhom4 bai5 txt khotailieu

- There are seven: Bell, door switch, window fail, passive infra-red detector, pressure mat, sense circuit and key-operated switch control box.. Now read this text to check which of you

Alarm Systems D8-DTVT2 Group 4 :

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:

1) What does this diagram show a circuit of?

- It’s a alarm system to use at home.

2) 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

3) What warning device does it show?

- It show about light and voice (bell)

4) 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 do this

5) 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

6) 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 2 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

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 2 on page 53?

- It will be adjusted the sensivity of the input

4, Use words from the text to complete the following table:

Energize De-energize

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