IEC 60839-11-5:2020 specifies the Open supervised device protocol (OSDP) for electronic access control systems. This includes communication settings, commands and replies between the ACU and the peripheral devices. It also includes a mapping of mandatory and optional requirements as per IEC 60839-11-1:2013 as covered by Annex. This document applies to physical security only. Physical security prevents unauthorized personnel, attackers or accidental intruders from physically accessing a building, room, etc.