The 24 controller incorporates cutting edge moisture sensing technology to prevent over-watering. The SC Series employs Acclima Digital TDT® moisture sensors with many easy-to-use features for optimum irrigation efficiency. The controller operates based on soil moisture measured by Acclima Digital TDT® moisture sensors. You set up programs similar to traditional timers; however, the SC Series only waters if the plants need it. Each zone can be set to one of two modes of operation: as a sensor controlled zone, or as a timed zone. The SC24 easily accommodates both drip zones and spray zones. The SC24 has the ability to set, maintain and monitor any desired moisture level. During the hottest part of the year, the controller might water every day. Then when the temperature cools, or you get a rainstorm, the controller prevents zones from watering until the moisture level in the ground falls below the moisture threshold you have set. Multiple zones can be watered simultaneously and Acclima's flow control optimizes the use of your water source.