I installed it on my first ride with my 43ft fifth wheel and it saved me the first time. The monitor is located on the dashboard in the cockpit of the F250. The distance from the monitor to the rear wheel is about 35-37 feet. I held the monitor about 60 feet from the sensors and the signal was still perfect. Relay sensor is not required for this article. Driving through Death Valley, California in temperatures hovering in the 100s, it warned me that my PSI tires were getting too high. This allowed me to adjust the tire pressure. Then, driving home at the end of the trip, I saw that one of my tires had lost pressure. I kept checking the pressure while driving to make sure I was in the safe zone. About 5 minutes after I got home the alarm went off to warn me of low pressure. After checking the tire, I found a large nail on the edge of the tread that required a new tire. Knowing this, I was able to change the tire before towing my 5th wheel to our camp. The instructions are a bit difficult to follow, but after playing around with the sensors for a few minutes I was able to reprogram them to show their location. on my trailer. I took them off on the ride and checked their accuracy with a digital tire pressure gauge; They showed the same pressure.