Antitheft Motion Sensor: Description and Operation

Location Shown On Model 203.0:

Task
To monitor the interior of the vehicle.

Design
The IMS[IRS] transmitter and receiver consists of an ultrasonic transmitter and receiver, and a microcontroller with data interface.

Function
with code 882 (interior motion sensor) or code 491 (USA)


Functional principle
The interior motion sensor transmitter and receiver (A26/14) uses ultrasonics to monitor the interior of the vehicle.

Activation/Deactivation
The unit is activated and deactivated by means of commands from the rear SAM control module with fuse and relay module (N10/2) delivered via the data interface.

Interior motion sensor with ultrasonics
When operating, the unit's transmitter emits ultrasonic pulses.
These pulses are reflected by the walls and objects inside the vehicle.
The reflections are registered by the unit's receiver and interpreted by a microcontroller. The reflection pattern changes when objects in the interior are moved. In this way, the unit detects manipulations in the vehicle and can trigger the alarm.


NOTE: In model 203.2 the left rear window glass breakage sensor (B39), the right rear window glass breakage sensor (B39/1) and the rear window glass breakage sensor (B39/4) (also in model 203.7) are connected to the interior motion sensor transmitter and receiver (A26/14). The glass breakage sensors are activated and their data interpreted by the interior motion sensor transmitter and receiver (A26/14).