Abstract: A remote alarm system that includes short range personal portable transmitter devices, which can be manually actuated in order to transmit a predetermined warning signal, and a plurality of fixed receiver devices disposed at suitable locations on a site to be protected, the said receiver devices being suitable for receiving the warning signal transmitted by any one of the portable devices located within range and transmitting the warning thus detected to security personnel.This system is more especially intended for the users of public places and public transport such as, for example, the underground railway.