Activities

Reading comprehension

The objective of this activity is to practise the comprehension of a written text and write the answers in well-structured and complete sentences.

Read the following text and answer the questions below.

Alarm systems

Home security is becoming increasingly important in those days. In the past, when house doors remained opened to strangers for most of the day, nobody thought of installing an alarm. But times have changed. The increase in the number of break-ins in houses, shops and buildings have made the installation of burglar alarms necessary. Apart form burglar alarms (also called “intrusion alarms”), official buildings must also have fire alarms to warn people of the presence of fire and to minimize its effects. Museums, banks, prisons and military premises have sophisticated, high-protection alarm systems.

An alarm is a system which is typically composed of a sensor or sensors, a control panel and an alerting device. Sensors are usually mounted on a door or a window so that the alarm is set off when someone opens the door or the window, but there are other type of sensors that detect intruders in or around a building by means of ultrasound, electric or magnetic fields. A transmitter emits waves. When someone enters the area protected by the alarm, a receiver in the sensors detects either an interruption of the waves or a change of frequency, depending on the type of waves emitted, and this sets off the alarm. Infra-red sensors detect the body heat of anyone crossing in front of the sensor.

The sensors are usually connected to a control panel with wires, but nowadays the wireless connections are more widely used because they are safer. A wired alarm could easily be disconnected merely by cutting the wire. However, wireless connections have the disadvantage that they use battery transmitters, and batteries must be continually supervised to allow a reliable signal to reach the control panel. In order to benefit from the advantage of both types of connections, there are hybrid systems which use wired and wireless connections.

The control panel is mounted on the wall inside the house or the room which is protected by the alarm. The panel allows to set the period of time in which the alarm will be on operation as well as connecting or disconnecting the system. When the sensor detects an intruder within the area, the control panel receives a signal which sets off the alerting device to warn people of the unwanted presence.

The alerting device typically consists on a loud bell or siren whose function is to frighten away the intruder. There are also silent alarms. They do not emit any sound, but send a signal to the nearest police station or private security company, usually through telephone wires, who are warned of the presence of an intruder in the area where the signal originated. The objective of silent alarms is to give the police or the security guards a greater chance of arresting the intruder. More sophisticated alarms, as for example those used in museums, banks and other robbery-sensitive buildings, include additional features like isolating a room with security doors and windows once the intruder is inside to prevent him/her from escaping before the police arrives.

Some burglar alarm systems in large buildings also include a closed-circuit television (CCCTV) with video cameras that transmit a signal to one or several monitors installed in a control post. The objective is to monitor the movements of the intruders and get images to facilitate identification.

Other types of alarm may have other features. Fire alarms, for example, are connected to water sprinklers distributed throughout a building. The sprinklers set off when the sensors detect smoke or fire to minimize the effects. Fire alarms may also cause security doors to close automatically to isolate the area and prevent fire from spreading to the rest of the building.

Comprehension questions:

  1. Why are alarms necessary nowadays, according to the text?
  2. What are the components of an alarm system?
  3. What are the advantages and the disadvantages of wireless connections compared to wired connections?
  4. When does the signal of the control panel of a sensor set off?
  5. What kind of alarm would you install in your house? Justify your answer.

  1. Alarms are necessary nowadays due to the increase in the number of break-ins in houses, shops and buildings.
  2. The components of an alarm system are: a sensor or sensors, a control panel and an alerting device.
  3. The advantage of wireless connections is that they are safer than wired connections, since they could easily be disconnected merely by cutting the wire. On the other hand, wireless connections have the disadvantage of using battery transmitters, and batteries must be continually supervised to allow a reliable signal to reach the control panel.
  4. The signal of the control panel of a sensor sets off when it detects an intruder within the area, then the control panel receives a signal which sets off the alerting device to warn people of the unwanted presence.
  5. I would install an alarm system with video cameras so that I could monitor any movements of the intruders and get images to facilitate identification.

A telephone conversation

The objective of this activity is to practise the language commonly used on the telephone.

Complete the following telephone conversation in an appropriate way by looking at the context and following the instructions in brackets.

You work at the law firm Larson&Sons. Mr Malcom Morris, from British Toys Inc., calls your office to talk to your manager, Mr Larson.

You (answer the phone): (1) …

Mr Morris: Good morning. This is Malcolm Morris, from British Toys. May I speak to Mr Larson, please?

You: (2) …

Mr Morris: Really? Do you know when he’ll be back?

You: (3) …

Mr Morris: Two weeks? I can’t wait so long!

You: (4) …

Mr Morris: No, no message, thank you. Is his son Matthew there?

You (don’t understand): (5) …

Mr Morris: I asked you if Matthew Larson was there.

You: (6) …

Mr Morris: Good. Could I talk to him?

You (connect to Matthew): (7) …

Mr Morris: Right, thank you. Bye!

You: (8) …

Suggested answers:

(1) Larson&Sons. Hello!

(2) I’m afraid he’s not in his office now.

(3) In two weeks

(4) Can I take a message?

(5) Sorry. Could you repeat that, please?

(6) Oh, yes, he is.

(7) Yes, I’ll put you through.

(8) Bye

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Electrical installations
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Self-correcting exercises