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SUPPLEMENTARY RESTRAINT SYSTEM (SRS)
3
SRS
11.1.2 WORKING OF RESTRAINTS
A. RESTRAINTS WITHOUT AIRBAGS
This restraint systems falls under the category of
Primary restraint systems.
PRIMARY RESTRAINT SYSTEM
Seat belts are known as primary restraints systems
as they provide the basic safety to occupants during
driving or accidents.
WORKING
The basic purpose of seat belts is to control occu-
pant movement inside the vehicle during driving
conditions, abrupt braking or accidents. They help in
avoiding or reducing the contact severity of occu-
pants with vehicle interiors.
It is necessary to wear the seat belts by the occu-
pants before starting to drive the vehicle. The seat
belts have a retractor mechanism which ensures
only the required seat belt webbing length is avail-
able for occupant usage. This reduces the risk of any
loose webbing over the body of occupants. The seat
belts have a locking mechanismwhich gets activated
in relevant conditions thereby preventing any loose
belt webbing to come out of retractor. This phe-
nomenon helps in controlling occupant movement
inside the vehicle.
COMPONENTS
1. Seat belt
2. Micro switch
3. Indicator lamp in cluster
B. RESTRAINTS WITH AIRBAGS
This restraint system falls under the category of
Supplementary restraint system.
SUPPLEMENTARY RESTRAINT SYSTEM
(SRS)
Air bags are the secondary restraint system as no
action is required by the vehicle occupant for the
activation of air bags.
!! WARNING
Seat belts shall be worn by every occupant when
ever they ride a vehicle. This is applicable whether a
vehicle is equipped with supplementary restraints
systems (SRS) or not.
WORKING OF SRS
Whenever there is an accident the sensor mounted
remotely sends crash signal to the ECU. The type of
accident and its severity, determines the time-to-fire
airbags in the system. The basic function of an air-
bag is to provide cushioning effect to occupants.
There are remote sensors mounted for sensing dif-
ferent frontal accidents. These sensors are con-
nected to the electronic control unit (ECU) of the
system. When an accident event input signal crosses
a pre-defined threshold level in ECU, the ECU trig-
gers the relevant restraints components in the sys-
tem. This helps in providing necessary protection to
occupants. The airbags and seat belt pretensioners
get triggered through ECU signal. The load limiter in
the seat belts is a mechanical device which gets ac-
tivated when the forces on the occupant upper body
region crosses a defined force threshold limit.
!! WARNING
Vehicle fitted with airbags should only be fitted with
RPLL seat belts.
COMPONENTS
1. ECU
2. Front remote sensor
3. Air bags
Driver air bag
Passenger air bag
4. Clock spring
5. Airbag warning lamp