Design

Design

Central electronic module (CEM)




The central electronic module (CEM) (4/56) is the master unit for the alarm.
The control module communicates with directly connected units, via the LIN and the controller area network (CAN). The control module has a number of sensors connected to it and determines what actions should be taken.

Switches in the lock units




A contact breaker is mounted in the lock units on the side doors and trunk lid/tailgate to indicate if any of them are open or closed. On vehicles with an alarm there is a single switch on the hood. The switches are closed when the door or tailgate/trunk lid is shut.
When the alarm is activated, the central electronic module (CEM) checks every 3 times / second that the switches are closed. If the central electronic module (CEM) detects that a switch is open the alarm is triggered.
If the central electronic module (CEM) detects that a switch is not closed when the central locking and alarm activation command is received, the vehicle tilt sensor and motion sensor will not be activated. Similarly, no attention will be paid to signals from a contact breaker that is not closed on activation.

Siren




The siren is used as a sound source for the alarm function. The siren is mounted under the cowl. The siren is available with or without an internal vehicle tilt sensor. The type of siren mounted in the vehicle is market and customer dependant.
The siren sounds if the power supply or grounding is cut or if communication with the central electronic module (CEM) fails while the alarm is activated. The siren contains an internal battery which is charged when the ignition is on. This battery has capacity for 10 alarm cycles. The battery service life is limited and depends on the local climate. The siren must be replaced regularly. The battery cannot be replaced by itself. The alarm cause can be read from the diagnostic tool. This states what caused the alarm.
If the vehicle is equipped with a siren with a vehicle tilt sensor, the sensor is integrated into the siren. The vehicle tilt sensor reacts to changes in the angle of lean of the vehicle and transmits a signal to the central electronic module (CEM). While the vehicle tilt sensor is mounted in the siren it is counted as a separate unit. If the vehicle tilt sensor indicates that the vehicle is being lifted the central electronic module (CEM) must send an activation signal to the siren. In this case the siren cannot trigger an alarm by itself.
The siren is powered via a fuse from the central electronic module (CEM) The siren is grounded in the engine compartment.

Movement sensor (IMS)




The movement sensor (IMS) is located in the interior lighting lamp in the headlining. The movement sensor (IMS) is used to detect movement in the passenger compartment when the alarm is activated.
When the alarm is activated, the central electronic module (CEM) checks the sensor.
The sensor communicates serially with the central electronic module (CEM).
When the sensor is activated is transmits microwaves into the vehicle. The sound waves bounce back from the interior of the vehicle and the sensor react to changes in these reflected waves. The sensor is sensitive to air turbulence and therefore all windows must be closed in order for the sensor to work optimally without risk of a false alarm.

Note! Due to the sensitivity of the sensor, the alarm can be triggered if an external passenger compartment heater is used for example.

Mass Movement Sensor Module (MMS) (only XC60 with panorama roof)




The Mass Movement Sensor Module (MMS) is located in the tunnel console under the cup holder.
The sensor is used to detect movement, primarily in the front part of the passenger compartment, when the alarm is activated. For these vehicles the Movement sensor (IMS) is located by the rear roof light.
When the alarm is activated, a check of the Mass Movement Sensor Module (MMS) is done by the Central electronic module (CEM).
The Mass Movement Sensor Module (MMS) communicates serially with the central electronic module (CEM).
Mass Movement Sensor Module (MMS) uses microwaves to detect movements when the alarm is activated.

Alarm LED




The alarm LED is located on top of the dashboard. The LED is in the same housing as the sun sensor and twilight sensor. The LED is directly connected to the central electronic module (CEM). It is used to indicate alarm status.
When the alarm is activated, the central electronic module (CEM) checks all units and sensors. If everything is OK the LED starts to flash once a second.
If the alarm is triggered the LED starts to flash fast, approximately 6 times a second. When the vehicle is unlocked, it continues to flash until the remote key is inserted into the starter module or the starter button is pushed (applies only to vehicles with the keyless system installed).

Switch for reduced alarm




Switch for reduced alarm is located on the center console under the control unit for climate control. The switch is used to temporarily deactivate the vehicle tilt sensor and motion sensor functions. When the function is activated the doors are not deadlocked when the vehicle is locked. The function can only be connected up to one minute after the ignition has been switched off. If a longer time has passed the ignition must be turned to position I and back to 0 before the function can be activated.
The switch has an integrated LED to indicate when the function is activated. A message is displayed in the display in the driver information module (DIM).

Heart beat sensor




The heart beat sensor is mounted against the body, to the right, under the floor in the cargo compartment. The sensor is only on vehicles with the keyless function. The sensor senses vibrations in the body that are created by somebody's heart beat inside the vehicle. The sensor can be activated from the remote key using the information button.

Note! The heartbeat sensor does not trigger the alarm functions in the vehicle. The sensor only indicates that somebody is in the vehicle in the event of a request from the remote key/Volvo Personal Communicator.

The heart beat sensor is directly connected to the central electronic module (CEM) and communicates serially via LIN with it.
The sensor is powered via a fuse from the central electronic module (CEM) and is grounded in the body.

Remote key/Volvo Personal Communicator




The remote key is used to activate and deactivate the alarm. The vehicle's alarm is fully activated approximately 11 seconds after the vehicle has been locked using the remote key's lock button (as along as the reduced alarm function has not been activated). The alarm is deactivated when the vehicle is unlocked using the remote key button for unlocking the central locking system. There is a button on the remote key for triggering the panic function in order to attract attention in an emergency situation.

Note! (Applies only to vehicles with keyless function and heart beat sensor installed): There is a button on the remote control for reading off the vehicle's status and for activating the heart beat sensor. The status of the vehicle is indicated by LEDs on the remote key. For further information, see Function.