Abstract: A building has at least one security guard post to control the secured building exits, each of which has an unlocking instrumentality, without forbidding their emergency use. When activating the unlocking instrument to open a secured exit, there is a transmission of information to the security guard post and an initiation of a delay during which the security guard can forbid the opening of the exit. The unlocking instrument can also visually indicate events at the exit. The apparatus has an electro-mechanical lock, a sensor which is sensitive to motion of the unlocking instrument, a control line linking each door to be controlled to the security guard post, and a central electronic processing unit. A surveillance circuit responds to the sensor. A security circuit frees the unlocking instrument when a fault is detected.