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# 45 XXXXXX

New life for historic trams

1 Hong Kong With many over ninety years old, the trams plying (1) the streets of Hong Kong are more than just a mode of transport. A popular tourist attraction, these double-deckers (2) are also regarded with affection by those living and working in this busy city. Aging controls and outmoded safety standards, unfortunately, are no longer compatible with the hustle and bustle (3) of Hong Kong's traffic. The problem: how to update the tram control system to modern-day standards while preserving the tram's historic character?

2 With the old control system, the driver operates the motor contactors directly using switches in the cabin. This makes smooth acceleration and braking very difficult; passenger comfort and safety largely depends on the driver's skill. Consequently, the tram operators, Hong Kong Tramways, and the local office of Siemens Transportation Systems have worked together on a control system for the trams based on the SIMATIC S7 200 programmable logic controller (PLC)

.3 In the new system, the PLC receives analog inputs from the Master Control Unit (MCU) which forms the man-machine interface. The driver inputs driving commands into the MCU through a Driver Vigilance Device (DVD) which represents the familiar "dead-man's handle," a fail-safe device that issues a braking signal if the driver loses control.

4 A fast analog-to-digital conversion time of 25 sec ensures that the tram reacts quickly to the driver's commands. The PLC combines command signals with signals from proximity speed sensors to determine the timing sequence for switching the motor contactors and for brake activation. A dual-speed sensor system provides a high level of safety due to redundancy.

5 Responding to the speed demanded by the driver, the PLC uses its digital outputs to control the tram's speed. One set of digital outputs is assigned to the contactors controlling the motors, and another set to valves controlling the supply of compressed air to the air brakes.

6 Commenting on the benefits of the new system, Nelson Mok, Siemens transportation systems general manager, says, "Using the S7 PLC as the tram controller enabled us to precisely match control characteristics to the vehicle and to compensate for differences in the tram drivers' operating styles." Following extensive test and approval stages, Hong Kong Tramways are now refurbishing (4) the whole fleet (5) of 165 vehicles.

Roy O'Connor, Global Design News, September 1998

Vocabulary notes
1. to ply = to make regular journeys (used for buses and boats)
2. a double-decker = a bus / tram that has two floors
3. hustle and bustle = busy, noisy activity
4. to refurbish = to modernise
5. fleet (of vehicles) : flotte ( de véhicules)

UNDERSTANDING THE TEXT

1 Pick ING-forms in paragraphs 1 and 2 and say if they are :
* present participles which are the equivalents of relative clauses;
* (ordinary) nouns;
* gerunds ( =a nouns) used as subject of verbs;
* gerunds introduced by a link word expressing time;
* present participles expressing means.

2 Read paragraphs 1 and 2 and decide whether the statements are right or wrong.
* The text is about old trams which have to be modernised.
* The trams are used only by tourists.
* The problem is to modernise them but also to keep their historic character.
*With the old control system the driver's was very important….
* because the motor was placed in the driver's cabin.
* Hong Kong Tramways and Siemens have decided to use PLCs to modernise the trams.

3 Read paragraphs 3 to 5
a. Label the diagram. Use : - motors - brakes -sensors - Driver Vigilance device (DVD) - Master Control Unit (MCU) - Programmable Logic controller ( PLC)

b. Answer the questions.
* What is the man-machine interface called?
* What controls the PLC?
* What does the MCU receive inputs from?
* What is Driver Vigilance Device for?
* What is it the equivalent of in a conventional tram?
* The text mentions 25 sec. What does this refer to?
* Which information has the PLC to process?
* What does this command signal act on?
* How is high safety obtained?

4 Read paragraph 6
* What are the two main advantages of the new system?
* What has finally been decided by Hong Kong Tramways?

LANGUAGE STUDY

1 Oppose what a driver had to do with the old system, and what he does now. Use : whereas, while, instead of (+ING) e.g. The PLC determines the sequence for braking whereas the driver had to do it himself.

2 What are the advantages of the new system?
* From the passengers' point of view. Think about comfort, safety, speed, retaining the historic interest, etc.
* From the drivers' point of view. Think about ease, safety, accuracy, etc.
* Recast all these ideas using comparatives e.g The trams are as touristic as before The trams are better adapted to traffic than the old ones The old trams were less easy to drive than the new ones

3 a. Study how the following verbs are used in the examples: to allow, to permit, to enable, to avoid, to prevent … from
* The component's small size allows to install in anywhere.
* This enables the operator to stop the machine when required.
* Another sensor permits to detect the presence of …
* It prevents the motor from overheating.
* This design avoids fitting gaskets and seals.

b. Use the prompts provided to recast the sentences:
* Having smooth acceleration was impossible >> The old system / not / to allow
* Passengers wanted to feel comfortable >> The old system / prevent …from
* It was impossible to compensate for differences in drivers' operating styles >> The old system / not / to permit
* People regarded trams with affection >> The old system / not / to prevent … from
* " It is possible to keep the old trams >> The new system / to permit
* It is not necessary to buy new trams >> The new system / to avoid
* It is possible to modernize the old trams >> The new electronic system / to allow

4 Study the following words
* able (to do) = capable (of doing) <> unable - As this man is a very able technician, he will easily repair the unit.
* to be able to ( to replace "can") - They can produce 1,000 parts a day, with the new machines they will be able to double the production.
* to enable (somebody) to (do) = to allow - The new PLC enables us to control the circuit accurately.
* to disable = to deactivate, disconnect, set out of operation. - The motor must be disabled before any repair is being carried on.

Translate: - Un système de vision permet aux robots de travailler avec plus de précision. - Neutraliser le relais 1 avant le relais 2. - Tu ne pourras pas finir le travail ce soir. - Il est incapable de faire marcher l'appareil. - A disque dur rapide permet à l'utilisateur de gagner du temps. - Il faut attendre 5 secondes avant de ( before + ing) pouvoir ouvrir le capot de protection ( safety hood)

5 Some features of technical English
Read again paragraph 4 (A fast analog to digital…) and
a/ Pick up the compound nouns and compound adjectives
b/ Vocabulary: pick up words which mean: to make sure - a sensing device - to turn on - to supply - because of
c/ Use these elements to fill in the blanks Gears made of stainless steel (compound noun = ………………………….) fitted on some special pumps tend to destroy themselves ………… the absence of lubrication. Using PEEK, a new polymer for these gears, ……………..s resistance to corrosion and wear. This product is ………..…ed by Victrex USA Inc. (Adapted from Design News Sept 98, page 64)

6 Translate paragraph 4 into French

7 Written exercise. The following notes sum up the tram's operation.

a. Turn them into a paragraph
1- The driver (to use) a DVD.
2- This device (to be) similar ( preposition?) the old "dead man's handle".
3- Its aim is to stop the tram if the driver ( to lose) control.
4- The commands of the driver (to receive / passive) by the MCU.
5- The MCU ( to act) as the man-machine interface.
6- The PLC (to transform) the analog input
7- Then, the command signals and also signals from sensors ( to combine / passive).
8 - The tram's speed ( to control / passive) by (outputs / digital) from the PLC.

b. Improve your first draft.
* Link sentences 1 and 2 with a relative pronoun.
* Sentence 3 : replace "its aim is to" with "this is aimed at + ING"
* Sentence 4 : use a possessive case
* Link sentences 4 and 5 with a relative pronoun.
* Sentence 7: replace "and also" with "as well as"
* Link sentences 7 and 8 expressing consequence (use: : "THUS + ing")

8 Written exercise.
Explain why Hong Kong Tramways had to modernize the trams but why it was actually impossible to have new ones. (Write no less than 60 words)
You can use: the reason why it was / is necessary / possible…- thus making it necessary / impossible to … - it must have been / seemed / thought / said…. - and words taken from the previous exercises, particularly n° 1 and 3.

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