A system for detecting the presence of a train on a railway track comprising a plurality of sections (2a", 2b",..., 2n"), the system comprising: - a transmitter arranged to emit a main signal comprising a plurality of frequencies (f 1, f 2,...., f n) towards the plurality of sections (2a", 2b",..., 2n"); - a plurality of selecting devices (14a, 14b,..., 14n) associated respectively to the plurality of sections (2a", 2b",..., 2n") along the railway track and arranged to selectively allow passage of said main signal towards respective sections of said plurality of sections (2a", 2b",..., 2n"); - a receiver arranged to receive the main signal after having passed through the plurality of sections (2a", 2b",..., 2n"); - a control unit associated to said receiver arranged to perform an analysis of said received signal so as to detect the presence of a train on a predetermined section (2a", 2b",..., 2n") of said plurality of sections (2a", 2b",..., 2n"); wherein - the transmitter is arranged to firstly concentrate all its power on a first carrier at a first frequency (f 1) for a predetermined first time interval, then to move to a second carrier at a second frequency (f 2) for a predetermined second time interval, then to go on through the frequencies of the plurality of frequencies until to complete the sending of all the frequencies of the plurality of frequencies (f 1, f 2,..., f n); - the plurality of selecting devices (14a, 14b,..., 14n; 15a, 15b,..., 15n) comprises electronic switches associated respectively to the plurality of sections (2a", 2b",..., 2n"), each electronic switch being arranged to allow the passage of the main signal on a respective section of said plurality of sections (2a", 2b",..., 2n") for only a time interval wherein the main signal has the corresponding frequency (f 1, f 2,..., f n). - a transmitter arranged to emit a main signal comprising a plurality of frequencies (f 1, f 2,...., f n) towards the plurality of sections (2a", 2b",..., 2n"); - a plurality of selecting devices (14a, 14b,..., 14n) associated respectively to the plurality of sections (2a", 2b",..., 2n") along the railway track and arranged to selectively allow passage of said main signal towards respective sections of said plurality of sections (2a", 2b",..., 2n"); - a receiver arranged to receive the main signal after having passed through the plurality of sections (2a", 2b",..., 2n"); - a control unit associated to said receiver arranged to perform an analysis of said received signal so as to detect the presence of a train on a predetermined section (2a", 2b",..., 2n") of said plurality of sections (2a", 2b",..., 2n"); wherein - the transmitter is arranged to firstly concentrate all its power on a first carrier at a first frequency (f 1) for a predetermined first time interval, then to move to a second carrier at a second frequency (f 2) for a predetermined second time interval, then to go on through the frequencies of the plurality of frequencies until to complete the sending of all the frequencies of the plurality of frequencies (f 1, f 2,..., f n); - the plurality of selecting devices (14a, 14b,..., 14n; 15a, 15b,..., 15n) comprises electronic switches associated respectively to the plurality of sections (2a", 2b",..., 2n"), each electronic switch being arranged to allow the passage of the main signal on a respective section of said plurality of sections (2a", 2b",..., 2n") for only a time interval wherein the main signal has the corresponding frequency (f 1, f 2,..., f n).