The 3 Range Switch Module (3RO) is a circuit board (CB) with a 3 position rotary switch. This option allows the user to select which range to view, and to set for alarm/control function. The 3R may be configured - via select switches - to disable or stop the alarm/control function from operating when changing ranges. The 3R will function with all Conductivity/TDS and Resistivity models, analog or digital.