Armed

Armed

adj. A perimeter door or device ALARM in it's “on” or enabled state. That is, the ALARM is set to shriek both locally and at the main panel in the control room if any attempt is made to open the associated door or access panel without using the KEY—on the ALARM first, and then on the door: “Don't open that—it's still armed.” See ALARM. See also DOOR SEAL.

NOTE: Door ALARMS show no visible lights or other indicators when Armed, because Armed is their normal state—the way they're supposed to be. However, a small red light beside the ALARM'S activation KEY slot turns on when the ALARM is dis-armed, or turned off.

Now, at first it may seem backward that a red light means “go,” as in, “it's safe to go through this door,” and no light at all means “stop—don't”—at least until you pause to consider whom that little red light is warning about what.

In this case, “Who” is whomever is responsible for the door—which certainly includes you. However, that responsibility primarily falls on the DEPARTMENT MANAGER and/or the M.O.D. “What” is the risk of uninvited guests and/or theft or SHRINK.

So a red light really still means “Stop!” but the rest of the sentence is, “...Don't forget to turn this ALARM back on again!”