Few years ago but i seem to remember the sensor at the top of the "B" pillar (drivers side) on the Gsi could be turned off for internal operation. There is a small cover which can be pressed to turn it off on the sensor cover.
Only reason i can remember is i have a dog who was forever setting the alarm off.
take care brian
ps this is on the Gsi not aware if it applies to other VX modles.
Hazzy is absolutely right; to quote the drivers manual : -
"Press button on ultrasonic sensor on drivers side; LED flashes at regular intervals for a maximum of 10 seconds.
Close doors.
Switch on anti theft system. LED lights up for 10 seconds: The system is now activated without passenger compartment monitoring."
This means that you can leave the windows or sunroof partly open without a passing breeze setting off the alarm.