Patent GB-589332-A (GB)
Title: Improvements relating to remote control systems
IPC: B61L7/08
Filed: 1943-02-15
Abstract: 589,332. Electric signalling and remote control systems. WESTING. HOUSE BRAKE & SIGNAL CO., Ltd. Feb. 15, 1943, No. 2460. Convention date, Aug. 21, 1942. [Class 40 (i)] [Also in Group XXXIX] A remote control system applicable as a centralised traffic control system for railways comprises a. control station connected to a number of remote stations which are capable of transmitting a multiple impulse code and a. central office, connected to the control station, having a code receiver. Upon the reception of a predetermined number of impulses constitut. ing a complete code, a stick relay at the control station is released, the other remote stations being unable to transmit codes until this relay has been released. A relay at the control station repeats the codes from the remote station to the central office and also controls an arrangement which releases the stick relay on the receipt of the first impulse of a code. General lay-out ;-The system comprises a central station, Figs. 1A or 1B, connected by a line to out stations, such as the station coding unit, Fig. 2A, which are controlled by and. send indications to the station coding unit shown in Fig. 1A by D.C. codes. The line also comprises one or more remote sections such as Y2, Z2, Fig. 2B, on which are stations controlled by A.C. codes from the station coding unit shown in Fig. 1B and converted into D.C. codes at the repeating station, Fig. 2B, at which the line sections are isolated'by filter VF. Indication D.C. codes from stations on the remote section are repeated in A.C. form over the line section Y1, Z1 to the office coding unit 2B The coding units are similar to those described in Specification 415,787. D.C. codes are of normal and reversed polarity respectively for control and indication, different frequencies being used in the case of A.C. codes. The office transmitter takes precedence over stations, and station transmitters have an order of precedence dependent on the priority of the Codes, and any station transmitter that has been locked out can be re-started from the central office. The station and office coding units are connected by filters to the line which may be used for telephony ; the filters LF at the stations have their condensers normally disconnected to improve voice-frequency transmission. The D.C. signalling circuit comprises bridged batteries 80, Fig. 1A, line windings of transformer 40, contacts of transmitting and pole-changing relays OT, PC, the line, contacts of master and transmitting relays M, T, Fig. 2A, at the stations and line relay R. The station transmitting relay T operates by short-circuiting the station side of the filter LF, and the result. ing pulse in the secondary of transformer 40, Fig. 1A, operates stick relay OR which when de-energized remains in its last set position. Modifications of the prior system, resulting from the use of coupling transformers 40 and the two-position stick relay OR, for reception at the office, Fig. 1A : Relay OR normally has its contact in the position shown, but if a line fault causes a change-over, it is necessary to restore the circuits to normal. A change-over from normal causes operation in turn of the relays OL1, OL2. OLP, OLB, OLBP used for timing the code elements in the prior system. If OR remains in this condition for an excessive time, all the relays except OL2 fall back; the relapse of OLBP completes a circuit over the lower winding of OR to restore it. The change-over of OR also operates the pole changer PC which is held by OLBP and reverses the line connections to release the polarized line relays R at the stations. This causes a similar cycle of operations of timing relays L1, L2, LP, LB, LBP at the stations, relay M being prevented from operating by L1. or L2 to prevent initiation of indication codes at this time. The pole changer PC restores when OLBP is ultimately released. When OR restores, OLI re-operates followed by the remaining relays ; all the relays then relapse. Corresponding operations at the stations occur when PC restores. The effects of faults during transmission of a code will be described later. Transmission and reception of a D.C. control code takes place substantially as described in Specification 415,787. The code push-button operates 1ST followed by STP and OM which (a) shunts the upper winding of transformer 40 to prevent operation of OR (the receiving relay) by transmitted codes, (b) disconnects 'the polechanger PC and (c) connects up the transmitting relay OT which is operated by the coding unit, as described in the above-mentioned Specification, the code being repeated to the coding unit at the station by line relay R, Fig. 2A. Transmission and reception of indicating codes :-A change in condition of a station device picks up start relay ST which, if line relay R is steadily operated (not receiving a control code ; relays L1, L2 unoperated), operates M. This relay (a) shunts the line to initiate operations at the office by reversing the line relay OR thereat, (b) connects up the filter condensers, (c) connects up the transmitting relay T and (d) reverses the connections to line relay R so that it releases and subsequently responds to battery reversal at the office. The office and station line relays OR, R start the operation. of a timing group OL1, OL2, OLP, OLB, OLBP at the office and a similar group, without prefix O, at the station ; the office pole-changer PC reverses the line polarity to release the R relays at all stations other than the transmitting station. Relays OR and R thereupon respond to the code transmitted by T and on the last step (16th) of the code, relays O16 at the office and 16 at the station, of counting chains thereat, pull up and OR, R assume their normal positions. At the office, the pole-changer PC restores normal polarity and relay 16 at the station releases M to restore the normal connections to R. Preventing interference of codes ; priorities:- As already described a code cannot be initiated until the line relays are normal. Further priority is given to the central office by making the first element of a control code long, that element of the indicating code from a station being short. Thus, the line is held open at the office until relay L1 at the station has been operated. and released, and since relay 1 of the chain at the station is operated on the 1st step, E picks up and restores M (if operated by initiation of an indicating code) which holds E and restores the station to receiving condition. Moreover, interference between stations which have initiated transmitting conditions but have not actually started sending is prevented by the release of the line relays at more distant stations by the shunt imposed by relays M and T at a nearer station. If, however, simultaneous sending does occur, this proceeds so long as the codes are identical, priority being then given to the code having the first long element in the remainder. Assuming station 2A to be transmitting an inferior code, T is released while R is still shunted by the T relay of the superior code so that E pulls up and restores receiving conditions as described above. If a station has more than one indication code stored, it is prevented from sending a second code until any other station with a stored code has sent it. Relay S pulls up at the end of the station identifying portion of the code and SS on termination of the complete code. When the station sending equipment is restored after transmission, SS is de-energized, but is slowreleasing so that the start circuit controlled by ST is held open until another station has started up, whereupon relay SS becomes reenergized and is held picked up for the duration of that code by the closing of the contacts of relays L2, LPB. Remote control by transmission of A.C. codes:-The coding unit, Fig. 1B, of the central office is the same as Fig. 1A except that it is connected to a repeating relay set instead of to the line. In this set, normally operated polarized relay PR repeats the code by following OT and removing a shunt on the output of oscillator OSC of frequency f1 from which A.C. codes pass over filter F1 to the line. At the remote repeating station, Fig. 2B the code signals are passed by filter F1, amplified and rectified at AMP and used to control relay 1CR which repeats the codes over line, Y2, Z2, in D.C. form. The line circuit of the remote section Y2, Z2 including bridged battery 80a is similar to that of Fig. 1A, the battery being shunted by contacts of 1CR. Relay 1PCP is energized by 1CR and remains held during code sending to maintain line relay 1R (over its lower winding) in normal condition so that the pole-changer 1PC cannot operate ; L remains normally energized. The distant stations are equipped as in Fig. 2A. Repetition and reception of indication codes from remote stations:-At the repeating station, Fig. 2B, D.C. codes from the remote stations control stick relay 1R, the pole-changer 1PC being operated at the commencement of transmission as and for the purpose previously described in connection with direct D.C. transmission from a station. Relay 1R controls a shunt on the output of oscillator OSC of frequency f2 which is connected to line Y1, Z1 over filter F2. The resulting A.C. code signals are received and rectified at AMP, Fig. 1B, and control polarized relay OCR which repeats the code to OR. The initial operation of OR starts the timing relays OL1, OL2, OLP, OLB, OLBP and operates the pole-changer PC, whereupon polarized relay NR and relay TA in the line circuit pull up. When transmission terminates and 016, Fig. 1B, operates, NR and TA release in succession due to the relapse of the pole-changer PC. When TA operated, relay NR took over from PR the function of shunting the output of oscillator OSC ; the successive release of NR and TA therefore transmits a pulse of A.C: to the repeating station, Fig. 2B, to operate 1CR and release the pole-changer 1PC. This A.C. pulse is not