The system consists of the ultrasonic sensor and the alarm control siren that is a combined control unit and self powered siren.

The ultrasonic sensor uses the ultrasonic Doppler technology. It saturates the volume of the vehicle with 40 kHz ultrasounds, convert the received signal that is generated by any moving target inside the volume into a rectangular wave characterized by the Doppler frequency, which is analyzed by a dedicated algorithm, in-built the microcontroller.

The alarm control siren communicates with the ultrasonic sensor and the MICU. If the alarm control siren receives an arm command from the MICU, it enters the arm mode.

If the alarm control siren receives alarm command from the ultrasonic sensor or the MICU during arm condition, alarm control siren activates the internal siren.

The system has the power supply line ‘+B Tamper' function (cutting wire protection). If one or both power supply wires (+B, GND) are tampered during arm condition, the system changes to alarm mode. If the alarm condition remains, the alarm control siren will trigger in alarm 10 times (programmable in EEPROM memory).

The system has the serial line ‘alarm comm line tamper' function (not authorized disarm attempt. If wrong identification code is received by the ACU, the system changes to alarm mode. The alarm control siren will generate up to 10 alarm triggers for each arm cycle (programmable in EEPROM memory).

The system has the serial line ‘alarm comm line polling' function (connection monitoring). If this wire is interrupted during arm mode the system change to alarm condition. If the alarm condition remains, the alarm control siren will trigger in alarm 10 times (programmable in EEPROM memory).