FIELD: protection and warning facilities, protection of important objects. SUBSTANCE: in accordance with invention centralized security service can be included as component of automated warning system. Device to form alarm signal has mobile spring-loaded plate which one end is located in key passage. Ends of this and another plates are positioned one opposite another and are fitted with mechanical catches. Hermetically sealed reed relay and constant magnet mechanically coupled to rest of mobile spring-loaded plate are attached to body of lock. Salient feature of method consists in sending of alarm signal by way of switching of contacts of hermetically sealed reed relay by field of constant magnet moved by mobile spring- loaded plate while key or skeleton-key is withdrawn from key passage if lock was not opened either by skeleton-key or key. EFFECT: simplified design of device and raised efficiency of method. 3 cl, 1 dwg
