Figure 23(a) Panel Detail. The diagram illustrates the symbols used for the following control buttons: floor numerals and letters, main entry floor (star), door closed (two arrows pointing together), door open (two arrows pointing apart), emergency alarm (bell symbol), and emergency stop (X within an octagon). The diagram further states that the octagon symbol for the emergency stop shall be raised but the X (inside the octagon) is not. The numeral height for floor indicators and symbols is 5/8 inch (16 mm) and the control button diameter is 3/4 inch (19 mm).