For TOP SECRET systems, agencies using infrared keyboards must not allow any of: (1) line of sight or reflected transmissions reaching an unsecure area; (2) several infrared keyboards of differing classifications in the same area; (3) any other infrared devices in the same area; or (4) infrared keyboards in areas whose windows lack a permanent means of blocking infrared transmission. The rationale notes that curtains which can be opened do not count as permanent blocking.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.