The system is very useful to situations when, while entering a place, someboby is boarded by a criminal that intends to take advantage in this moment to get into that place.

When the alarm is activated, a central office is informed about the happening and the right security actions are taken to prevent personal and pecuniary damages.

The user has two keys (fig 1), a short one (1) and a long one (2). The system works with simple keys (these with grooves) or standard"yale"type (these with four grooved sides).

When the short key is used (1) the mechanism activated is the usual lock system (fig 2), since its reach is not enough to cross the edge of the mechanism, thus failing to trigger it (4 or 5, depending on the side of the key that is introduced).

When the longer key is used (2), both mechanisms, the normal lock system and the alarm system, are activated due to its longer (2) extension (3). It reaches the free area (6) between the edges of the mechanisms of the lock marrow (4 and 5) thus triggering an alarm by mechanic, eletric, optical or another activation system, preferrably noiseless and remote.