FY 901 is a “circle” enclosed in a “square,” which indicates it is an instrument that has a shared display or a shared control. The “901” is the “loop number.” The “F” indicates this is “flow” related, and the “Y” is saying there is some kind of conversion or computation going on. The way we know it is a “time related” conversion is from the “f(t)” notation at the top right hand corner of the box. The output of FY 901 equals the input times some function of time or equals some function of time alone.