Hi5 controllermaintenanceHi5 Controller Maintenance Manual4. Basic Components of Controller4.3. The Function of Each Component4.3.1. Rackand Backplane Board (BD501)On this page4.3.1. Rackand Backplane Board (BD501)4.3.1. Rackand Backplane Board (BD501) 4.3.1.1. Outline