T20 units are simple, reliable float switches, designed for top mounting into tanks or vessels. T20 units utilize a single switch mechanism and float. It can be used for virtually any type of open or closed process or storage vessel, with either threaded or flanged type mounting, and actuating depths of up to 48 inches (1219 mm). T21 units combine the functions of two separate narrow differential level controls in a single, compact, easy-to-install instrument. Two independent switch mechanisms are employed to provide two actuating levels at least 8” apart, at actuating depths of up to 48 inches (1219 mm), for applications such as high and low level alarm operation. Model T21 tandem float switches are