Surprisingly, this inexpensive $22 motion detector alarm works pretty well. I spent over an over testing this 9 volt powered alarm, and I can tell you that while the alarm is mounted inside the van (and with windows up), the alarm will *NOT* give any false alarm from pedestrians walking by the sidewalk. <br><br>Finding the optimal position for where to mount the alarm inside the van is extremely important so that the detector will give the best results for detecting an intruder and sounding the alarm. Ideally, the best position is probably somewhere on the ceiling and having the sensor pointed slightly downwards towards the front of the dashboard and doors to detect any intruders. <br><br>However, since my van is a low-top, I'm wary to install any more items on the ceiling because I'm already constantly bumping my head on the flip down DVD player and other items. So after trying several different spots, I finally decided on mounting the alarm (for now) to the left upper side of my van wall with the sensor pointing diagonally towards the dashboard and windshield. Anyone that tries to enter through the passenger front door will cause the alarm to sound immediately. However, for the passenger driver side, an intruder would have to go slightly further into the van up to where the driver seat is which would then sound the alarm. <br><br>Actually, it's better for me this way because I have a little bit of room to open my driver side door, and raise my arm up to turn off the alarm before it starts blaring. The alarm has 2 settings for loudness which are "Alarm" and "Chime". The Alarm loudness is actually a bit ear piercing, almost as loud as a smoke detector alarm. Certainly loud enough for nearby neighbors or passerbys to hear the alarm if it goes off in the middle of the night. <br><br>I have attached a picture of where I have currently installed the alarm. I may change the position next time, but it works for me for the meantime. By the way, I'm only using this inexpensive alarm as a backup to my real alarm which is a comprehensive Viper alarm system. I'm not trying to mislead anyone to think that this $22 alarm would be sufficient as a cheap substitute for a "real" alarm.