Remain calm and obtain as much information from and about the person who is making the call.
Listen to and take notes from any peculiar background noise, or anything that could give a clue as to the place from which the call is being made/or the identity of the caller.
Immediately contact security.
Security and other personnel must maintain radio silence until the existence and nature of the device is determined.
Buildings should be evacuated to the areas listed under evacuation in the event of fire.