The invention comprises an intrusion-detection system based on a switch 1 that provides more effective protection by means of an innovative arrangement of three intrusion-detection contacts 16-17-18 on an electronic circuit, connected to two different intrusion-detection electronic circuit and an intrusion-detection switch 1 with a special design that provides three different interconnections between said contacts in response to different intrusion attacks. The special arrangement of the contacts on the electronic board provides protection against different sophisticated attacks even without the participation of the intrusion-detection switch.