11. Match the actions in Column a with an appropriate consequence from Column b. Then join each action and consequence using an if-sentence and making changes if it is necessary.

A

B

1. Alarm clocks are left unattended long enough. 2. The system or its particular part works badly. 3. People hear or see an alarm warning about a problem or condition. 4. Automatic fire alarm systems detect the unwanted presence of fire or smoke. 5. False alarms acclimatize people to ignore alarm signals. 6. The danger of natural phenomena approaches or has passed. 7. A car alarm is installed in a car. 8. Personal alarms emit a loud siren-like alarming sound. 9. Burglars enter a building or area. 10. Medical alarms detect smoke, an intruder or a low room temperature.

a) People flee the danger or attempt to eliminate it. b) It is possible for people to ignore an actual emergency. c) Sensors detect burglars by a lot of methods. d) Most alarm clocks automatically stop the alarm sound. e) A distributed control system generates alarms to direct the operator’s attention to an important event. f) Air raid siren generates sound to provide warning. g) Automatic fire alarm systems notify the building occupants to evacuate. h) A car alarm attempts to discourage theft of the car itself and its contents. i) Medical alarms begin working automatically to summon assistance to ill people’s location. j) Personal alarms attract attention and scare off an assailant.

Speaking.

12. Think about these situations and what you will do in each of them. Then talk to your partner and find out his ideas.

1. What will you do if you find that someone has used your computer without your permission?

2. What will you do if your friend lied to you?

3. You are traveling in the bus. What will you do if you see someone stealing a mobile phone from another person’s pocket?

4. What will you do if you feel very sleepy in the morning before going to university?

5. What will you do if spend all your money and don’t have any?

Writing.

13. Translate the paragraph which your teacher will give you.

Technical Reading.

14. Read and translate the text. Three stages of a simple alarm system.

The first stage is a sensing device that changes its resistance when it detects a particular from of energy. For example, a microphone can be used to detect sound, a thermistor to detect heat, or an LDR (light-dependant resistor) to detect light.

The second stage is an electronic switch. In its simplest form it could be a single transistor. The transistor switches between cut-off and saturation as the input resistance changes.

The third stage is an output transducer which is switched off and on by the electronic switch. The output transducer could be a buzzer, a light or a relay, which operates a more powerful circuit.

An example of a simple alarm circuit is shown in Fig.2.

The LDR forms the potential divider with the variable resistor RV1. When light falls on the LDR, its resistance decreases. This causes the base voltage of the transistor and the bias current to increase. The transistor switches on and there is a rapid rise in the collector current until the transistor goes into saturation. The increased current causes the relay to operate and switch on the output circuit. The sensitivity of the input can be adjusted using RV1.

In a similar way, the relay is de-energized when the light source is removed from the LDR. A large back EMF, which would destroy the transistor, could be generated across the relay. To prevent this, a diode is connected in reverse bias across the relay.