I also use the Lacrosse Technology unit. Model WS-7013U-IT It can be a little tricky setting it up. You have to load the batteries in the transmitter first. The sensor is located on the shady side of a 6 by 6 post. One sensor is in the greenhouse and the other in the master bath. The master bath is on the other side of the house so signals have to travel through the house. It works great. I picked it up a LL Bean Arnold