This part of IEC 60839 specifies the Open Supervised Device Protocol 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 F. This standard applies to physical security only. Physical security prevents unauthorized personnel, attackers or accidental intruders from physically accessing a building, room, etc. This standard does not in any way limit a manufacturer to add other commands to the protocol defined here.