We have the tst 507 on our 2010 Ram 3500 megacab and 39ft Keystone Alpine 5ver. Bought the booster but was not needed. It shows press and temp on all 8 tires. When we unhook trailer and drive TV it goes thru all 8 tires but only TV tires have readings. With trailer parked in front of our barn the trailer tires give readings as we drive the TV by on the road (about 100 ft from 5ver). It is a great system!!