ISIS headrests

• Active front headrests: the active front headrests reduce the dangerous distance between the back of the head and the headrest as early as the initial phase of the crash. The active front headrests are moved forward slightly in the event of a crash. The active headrests thus reduce the relative movement of the head in relation to the upper torso.
  
• Electrically extendable rear headrests: the electrically extendable rear headrests support the head to prevent ”whiplash” of the cervical vertebrae in the event of a crash. This can prevent the 'whiplash' syndrome (painful stretching of the neck muscles, tendons and nerves).
  

Brief description of components

Active headrests, front

The active front headrests consist of

• Slide element: the slide element is an inclined plane on which the headrest can be guided with a slider.
  
• Generator with priming cap: the priming cap drives the plunger.
  
• Plunger: the plunger moves the slider of the headrest.
  

If the ISIS system detects a crash of sufficient severity, the priming caps are ignited (by the SSFA and SSBF: satellite, driver's seat; satellite, passenger's seat). The plunger moves out and actuates the slider of the active headrest. The active headrest is guided forward on the inclined plane and thus supports the back of the occupant's head.

Rear headrests

Electrically extendable rear headrests are fitted with the special equipment

• Special equipment ”Side airbag for rear seat passengers, incl. head airbag and electrically extendable outer headrests” and
  
• Special equipment ”rear Comfort seats, with electric adjustment”.
  

With this special equipment (SE), the rear seat satellite (SSH) is installed. The rear headrests are not secured in the backrest but firmly mounted on the cross member of the rear shelf. As they are thus solidly attached, active movement of the headrests as in the case of the front seats is not technically feasible.

Control modules for the electric rear headrests: the activation of the electrical rear headrests is integrated in the satellite of the rear seat. The headrests can be adjusted with ”terminal R On” using the switches provided for the purpose. However, once they have been manually adjusted, they remain at this height until there is a terminal change ”terminal R Off” to ”terminal R On”. They then move to the position specified by the seat occupation detection. If SE ”rear Comfort seats, with electric adjustment” is fitted, the seat module controls the headrests.

Extending the headrests: the headrest on each side is extended when

• the seat occupancy recognition detects occupancy and
  
• terminal R is ON
  

Retracting the headrests: The headrests are returned to their home position when the headrest is extended and

• the seat occupancy recognition detects an empty seat or
  
• terminal R is switched off.
  

Deactivation undervoltage/overvoltage: The activation of the headrest motors is time controlled. The time can be coded. The headrests only move when the Safety Information Module signals normal voltage. In the case of overvoltage or undervoltage, the motors are not activated.

Fault messages: the motor control sends a fault signal in the case of overload and interruption.

Seat occupancy recognition, rear left and rear right

The seat occupancy recognition, rear right and left, is fitted with the special equipment ”side airbag for rear seat passengers, incl. head airbag and electrically extendable outer headrests”.

The signals of the link and right seat occupancy recognition are read in by the SSH (satellite, rear seat).

Control modules

The following control modules are involved in the message transmission for the battery headrests:

• Seat module for headrest adjustment rear left and rear right with special equipment ”rear Comfort seats, with electric adjustment”.
  
• SIM (Safety Information Module)
  
• SSFA (satellite, driver's seat)
  
• SSBF (satellite, passenger's seat)
  
• SSH (satellite, rear seat)
  

Service functions

Note on safety

All work on the priming caps of the active headrests and on the electric motors of the rear seat headrests must only be conducted with the battery disconnected.