An intrusion alarm-security system for detecting unauthorized entry of persons into a defined secure area within a building structure, for generating and transmitting signals responsive to such intrusion and for activating security systems in response to such intrusion signals, said system comprising:
- (a) at least one structural moment detector carried by a structural member of said building, located within said secure area, said structural moment detector generating intrusion signals responsive to the deflection of said structural member induced by changes of the loading on said member caused by an intrusion and being insensitive to linear distortions of said member;
- (b) means for transmitting said intrusion signals to a control center;
- and
- (c) means in said control center for receiving said intrusion signals and for generating security system activation signals in response thereto.