The Open Supervised Device Protocol (OSDP) provides an open and bi-directional communication link to HID iCLASS readers. Implemented over a multi-dropped RS485 hardware bus, OSDPenables host controller reader behavior, including visual (LED) and audio (beeper) indicators, full LCD control (iCLASS RKL only) and polling for card reads. Perfect for enhancing a time and attendance system, the OSDP enabled iCLASS LCD reader enables such functionality as displaying a ticking clock, personnel information and system notifications for user interaction at the door. .