Definition: Pretensioners are the part of a seatbelt that takes up the slack. Too much slack equals too much occupant movement in a crash, and a greater chance of injury.
There are three kinds of pretensioners in use today: mechanical, electrical and pyrotechnic.

Mechanical pretensioners use an inertial wheel and a pendulum mechanism -- they take up seatbelt slack, and only release it under slow, controlled pressure. Pull quickly, as in a crash, and the pretensioner locks the seatbelt in place.

Electrical pretensioners replace the pendulum with an electrical sensor, but still act in much the same way. Electrical pretensioners may be connected to the airbags, locking the seatbelts in the event of airbag deployment.

Pyrotechnic pretensioners are the latest (and most expensive) version of the technology.



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Note added at 7 mins (2007-11-09 15:53:55 GMT)
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زوائد الحماية الإضافية

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Note added at 8 mins (2007-11-09 15:55:16 GMT)
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وتختلف في انواعها

English term (edited): pretensioners belt

مشدات لأحزمة الأمان ومحددات متكيفة لقوة شد أحزمة الأمان
مشدات أحزمة الأمان الكهربائية

الجزء من حزام الأمان الذي يقبل الشد عند حدوث صدمة

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