Auto alarm system for mounting in the engine compartment, activated by remote control. The siren is characterised by its geometric design. The protective cover, which slides open for adjustment, is of the same colour as the siren body but translucent to allow inspection of the status lights during regulation. The remote control is formed in two parts made of different materials, but having the same colour. The rigid part contains the electronics while the more flexible part serves as a keyholder. Colour-coded buttons, identifying the various functions of the remote, are grouped on a prismatic axis to accentuate the operating direction.