Locking and Alarm Systems (page 7 of 9)

SECURITY

86-5-10 DESCRIPTION AND OPERATION

BBUS Harness Connector

BBUS Harness Connector C0666 Pin Details

Volumetric Sensor
The volumetric sensor is installed behind openings in the rear interior lamp and monitors for intrusion into the 
passenger compartment when the alarm is armed.

The volumetric sensor consists of a microcontroller, two acoustic transmitters and two acoustic receivers. One 
transmitter/receiver pair faces forwards and one transmitter/receiver pair faces rearwards to ensure complete 
coverage of the passenger compartment. The front transmitter/receiver pair are in a rubber mounting attached to the 
microcontroller housing. The rear transmitter/receiver pair are in a remote rubber mounting and connected to the 
microcontroller housing by a four wire lead.

The volumetric sensor is powered by a permanent battery feed from the passenger compartment fusebox. The BCU 
activates and de-activates the volumetric sensor when it arms and disarms the alarm system. When the volumetric 
sensor is active it outputs ultrasonic pulses from the transmitters and checks the echoes picked up by the receivers 
for changes to the passenger compartment profile. If it detects a change of profile indicating movement in the 
passenger compartment the volumetric sensor reports the alarm to the BCU.

Each time the volumetric sensor is activated it performs a self test. If there are no faults the volumetric sensor sends 
an acknowledgement signal to the BCU. If the BCU does not receive the acknowledgement signal it de-activates the 
volumetric sensor.

Pin No.

Description

Input/Output

1

Ground

–

2

Arm/Disarm signal

Input

3

Battery power supply

Input

4

Alarm activation

Input

M86 5979

C0666