Frame size:Button optional:1.LED : Red ,Blue,Yellow2.Diameter: 33mm3.Braille: with or without braille4.Voltage: DC 12V or DV 24V5.Number & Figure :-3,-2,-1.0.1.2...60,Door open,Door close ,Up arrow,Down arrow,Alarm,Telephone,G,B,P,B,B1,B2, etc6.Material :Frame in ABS ,surface in Stainless steel .7.Life: more than 5 million of operation time,OMRON switch8.Reference : OTIS elevator .
link:http://www.ds-elevator.com/ak-285a