2010 ADA Standards for Accessible Design Pocket Guide
407.4.8.1 Visible Indicators.
Visible indicators shall comply with 407.4.8.1.
Characters shall be ½ inch (13 mm) high minimum.
Indicators shall be located above the car control panel or above the door.
As the car passes a floor and when a car stops at a floor served by the elevator, the corresponding character shall illuminate.
EXCEPTION: Destination-oriented elevators shall not be required to comply with 407.4.8.1.3 provided that the visible indicators extinguish when the call has been answered.
In destination-oriented elevators, a display shall be provided in the car with visible indicators to show car destinations.