Unit16 text a Detection Devices

1.Read and memorize the following words and word-combinations and their translations.

1. Set off – включення;

2. Audible – те, що можна почути, відрізнити на слух; чіткий;

3. Cut off – виключення, вимикання;

4. Tamper – псувати;

5. Trigger – приводити в рух, починати;

6. Back up – дублювання

7. Buzzer – сигнал, гудок;

8. Saturation – насичення

9. Transducer – датчик, перетворювач.

2. Read and translate the following text.

Magnetic switches

These are used on windows and doors. A magnet mounted on the moving part of the window or door trips a switch mounted on the frame when the window or door is opened.

Break detectors

These are fitted on the inside surface of glass in windows and doors. Some use a thin metal foil which is glued around the edge of the glass: if the glass is broken the foil breaks too. Others are vibration sensors, and respond to the shock of the glass being broken.

Pressure mats

These are fitted under the carpet-at the bottom of the stairs, for example. The pressure of someone stepping on them causes two thin metal plates inside to come in contact, setting off alarm. Because they’re constantly being walked on, pressure mats get ‘tired’ quite quickly, and should be regularly tested and replaced if necessary.

Motion sensors

These may use passive infra-red, ultrasonic or microwave energy to detect movement within their range.

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 are 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, if an intruder disconnects the mains supply.

3. Translate the following word-combinations and memorize them.

Moving part, inside surface, metal foil, respond to the shock, come in contact, get tired, set time, reset automatically, disconnect main supply, sensing device, light-dependent resistor, single transistor, powerful circuit.

There are three stages of a simple alarm system. The first stage is a sensing device that changes its resistance when it detects a particular form of energy. For example, a microphone may be used to detect a sound, a thermistor to detect heat, or LDR (light-dependent resistor) to detect light.

The second stage is an electronic switch. In its simplest form, this 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 could be a buzzer, a light, or a relay which operates a more powerful circuit.