Patent GB-190706134-A (GB)
Title: Improvements in and relating to Signalling Systems for Railways and the like.
Filed: 1907-03-13
Granted: 1907-12-31
Abstract: 6134. British Thomson-Houston Co., [General Electric Co.]. March 13. Automatic systems; electric railways, signalling on. -In an automatic electric system of signalling on electric railways in which the track rails are electrically continuous for the power current, the adjacent sections being bonded together by reactance coils which serve to divide the track into sections so far as the signalling-current of a higher frequency is concerned, the signalling-circuits, with the exception of one circuit for exciting a relay winding, are all normally held open and are closed only by an approaching train momentarily closing a rail contact in the circuit of a self-holding relay, which completes the circuit to the transformer supplying energy to the track relays. By this means, there is no energy used in transformers and relay coils, except on those sections the condition of which is to be indicated to an approaching train. The system particularly described is shown diagrammatically in the Figure. The track rails are divided into sections A, A<2>, A<3> bonded in the known manner by the coils of transformers C', C', C<3>, D', D<2>, D<3>, of which the central points are connected and which serve to energize the rails and the relays F', F', F<3> from the signalling-current line-wires b, b<1>. The primary coils of the transformers C', C<2>, C<3> are in a normally open circuit, which may be closed by the armature m or m<2> of the magnets M<2>, M<3> &c. the circuits of which are controlled by the train operated contacts 1, 2, 3, &c. Normally no current is passing in the transformer or relay coils, except in the coil f' which is energized directly from the line-wires b, b<1> ; the signal-operating circuits are also normally open. A train passing over the short rail 1, whicu is shown as an example of a train-closed contact arranged at the entrance to a section, closes the circuit from the source of energy o<2>, contact 1, and lower rail A' to the magnet M' which draws its armatures. The armature m<1> closes a maintaining circuit ; the armature m' closes a circuit from the line b armature m<2>, primary winding of the transformer C', and line b<1>. The transformer C', therefore, energizes the transformer D', which is connected to the coil f<1> of the relay F'. The relay F' closes the signal-operating circuit for the home signal H' which is moved to clear, and closes the contacts h, h<1>. The contacts h are in series with the armature m, which is closed by the magnet M<2>, and with the transformer C<3> which is thus energized and through the transformer D<3> closes the relay F<3>, and causes the lowering of the signal H<3> for the next section ahead, if that section is clear and no rails are broken. The contacts h on this signal close the circuit to the magnet J' which moves the distant signal K' to 'clear.' No further action takes place until the train passes the contact 2 on to section A', thereby short-circuiting the magnet M', and also de-energizing the relay F' and putting the signals H<2>, K<2> to 'danger' behind the train. At the same time, the contact 3 is closed and energizes the magnet M<3> which controls the signals H<3>, K<3>. Although the circuit of the transformer C<3> is broken at the signal H<2> on its return to danger, the transformer at almost the same instant receives current through the armature m' of magnet M<3>, so that the signal H<3> does not go to danger' and signals for the next section are set as above described.