| 摘要 |
A device for detecting the unbalance DELTA i between the two fractions of the return traction current flowing in the two rails of a railroad track, in the presence of a signalling current in the respective track circuit, includes a linear combination circuit (3) that receives two signals (i1 and i2) which are proportional to the two currents actually present in the two rails and obtains both the difference (i1-i2) and the sum (i1+i2) thereof. A demodulating circuit (4), fed with the difference signal, takes from it the modulating signal of the signalling current and feeds it to a sample generator circuit (5), which generates a sample function M(t). The sample function is supplied to two successive sampling circuits (106 and 206), one of which also receives the difference signal and produces a sampled difference signal M(i1-i2), while the other also receives the sum signal and produces a sampled sum signal M(i1+i2). Four filtering-rectifying parallel circuits (107,207,307,407) receive the sum and difference signals and the sampled sum and difference signals, and supply the mean values Fo [¦i1-i2¦], Fo[M¦i1-i2¦], Fo[¦i1+i2¦] and Fo[M¦i1+i2¦]. A function generator circuit (8) furnishes an output signal corresponding to <IMAGE> which is supplied to a switching circuit (11) along with the sum and difference signals. The switching circuit is controlled so as to give, at the output thereof, one of the signals <IMAGE>
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