Patent GB-437654-A (GB)
Title: Improvements in electric signalling systems particularly for train describing purposes
IPC: B61L25/04
Filed: 1934-05-02
Abstract: 437,654. Electric signalling systems. MORDIN, R., and WESTINGHOUSE BRAKE & SIGNAL CO., Ltd., 82, York Road, King's Cross, London. May 2, 1934, No. 13307, [Class 40 (i)] In a train-describing system wherein descriptions are transmitted as coded impulses over a single pair of line wires, the code employed comprises one or more current impulses of a distinctive character distributed in a manner characteristic of the description in a series of impulses the remainder of which are of a different character. Provision also is made for permitting transmission of an impulse only after the preceding impulse has been properly received. Fig. 1 shows the equipment at the transmitter and Fig. 2 that at the receiver. Each indication to be transmitted is registered in a coder SC by the operation of appropriate keys (not shown), the coder being adapted to mark with positive potential the contacts 2, 3, 4 of a transmitting switch T in characteristic combinations in accordance with the indication to be transmitted. The switch T is adapted to transmit to line negative impulses for all unmarked contacts and positive impulses for the marked contacts and consequently a train description is characterized by the positions of the positive pulses in a train of impulses of fixed number. Transmission of impulses. When a train leaves the transmitting station the switch T is stepped off-normal and a relay IR is energized over the line wires L1, L2. In the absence of positive marking from the second contact of switch T relay RV remains inoperative and a negative impulse is transmitted to energize relay F at the receiver which operates the stepping magnet 19 of a paper ribbon adapted to receive a punched record of the train description. If, however, the engaged contact is marked with positive potential relay RV is operated and the polarity of the transmitter impulse is reversed to effect operation of relay P. The relay P operates, in addition to the stepping magnet 19, a punch magnet PM for punching the record. When either 19 or 19 and PM are fully operated and relay MC is operated to open the line circuit and release relays F or P and IR. Release of IR effects operation of switch T through another step a similar cycle of operation occurring at each step of the switch. The arrangement is such that each successive impulse can be transmitted only after the preceding impulse has become effective at the receiver. In the arrangement shown contacts 2, 3, 4 only are utilized for descriptions, the contacts 5 being employed for effecting spacing of the receiver ribbon while the next positively marked contact is arranged to define the end of the description. Recording, storing and display apparatus. The record strip 21a is fed over a punching plate 22 to form a loop which when of predetermined length operates a contact 27 to close the circuit of a shift magnet ST. and start the shift mechanism SM which draws the ribbon on to the decoding plate 32. When the stepping action of the shift mechanism is complete and a relay SH is operated and magnet TM is energized to lower the pins 37 into engagement with the ribbon 21 so as to select a combination of circuits 42 corresponding to the punched record. The receiving apparatus comprises three storage coders 39, 40, 41, which are associated with an indicator (not shown). The coder 39 is operated over the leads 42 and when operated relay CE is energized to release the magnet TM. Provided coder 40 is unoccupied, relay TR is operated to transfer the description from code 39 to coder 40 from which it passes automatically to coder 41. As each train leaves the remote point the corresponding train description stored in coder 41 is arranged to be cancelled by the energization of relay CL which is operated either manually by an operator or automatically by the passage of the train. Retransmission of descriptions to further remote stations. The coder 39 may be utilized for the immediate retransmission of the description contained therein the passage of the description from coder 39 to coder 40 being suspended till such transmission is completed. The outlets of coder 39 are normally connected over the back contacts of relay TR to the bank contacts of a retransmitting switch RTM which is started automatically when the coder 39 becomes occupied. When the transmission is completed relay TC is operated and relay TR is operated to transfer the description from coder 39 to coder 40. In a modification a further coder may be associated with the retransmitting switch in order that additional descriptions may be interposed at the receiver. In the event that a train leaves the transmitting station without a corresponding train description being set up, the train operates a local indicator and the local operator actuates a special key which controls relay RV and transmits the omitted description. Cancelling. A description registered at the receiver may be cancelled by transmitting a characteristic code and operating the coder 39 in such a manner that the description stored in any coder may be cancelled. In a modification the transmitted cancelling signal operates an alarm at the receiver and renders operative a " cancel " key which may be operated by an attendant at the receiver station. Transmitting descriptions of trains of a standard schedule. The descriptions of trains of a standard schedule are recorded on a record strip which is fed through a coding apparatus under the control of the departing trains. The coding apparatus is associated with a transmitting switch as already described. Transmitting descriptions of different classes of trains. A single pair of line wires may be utilized for transmitting two or more different classes of trains, e.g. fast or slow trains, by prefixing to the code signal constituting the description a discriminating impulse which differs according to the character of the class. Two-way working. A single pair of line wires may be used for transmission in either direction by the provision of an auxiliary relay controlling the connections of the line conductors to the transmitter and receiver at each point.