Fairly simple design, basically just a tire pressure gauge that constantly shows when the trailer is moving. Sometimes reading takes a little longer than we would like. Go to the device in the car. But the readings are easy to read in direct sunlight, and the solar power means I've never connected it to an external power source at all. I love that you can set the min/max PSI and overall tire temp for the alarm. towing a trailer and you don't want to constantly use a tire gauge at every stop to make sure your air values are okay, great little kit.