Rainbird ESP4SMTEI Smart Irrigation Controller - Indoor Rated he Rain Bird ESP-SMTe can grow with your landscape, easily expanding from 4 stations up to 22 stations. By comparison, the ESP-SMTe not only suspends irrigation, it measures instantaneous rainfall amounts, determines the effective rainfall and calculates exactly how much to adjust your watering schedule to prevent over-watering and under-watering. SP-SMTe customizes each zones irrigation schedule.