Patent GB-581909-A (GB)
Title: Improvements relating to remote control systems
IPC: B61L7/08
Filed: 1943-11-18
Abstract: 581,909. Electric selective signalling. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd. Nov. 18, 1943, No. 19270. Convention date, March 6. [Class 40 (i)] A remote control system applied to railway signalling &c. utilizes a pair of transmission wires extending completely around the system to which each station is connected and employs a code consisting of a series of impulses of alternately opposite polarity, the pauses between successive impulses being either long or short to determine the code character. Sixteen impulses at approximately six cycles per second are used in the code and the central office may control up to sixteen stations, each of which may transmit indications back to the central office. Codes transmitted by the central office have priority over those originating in controlled stations. Timing and counting. The equipment at the central office is shown in Figs. 1A and 1B and is connected to the common lines YZ by wires running through a low-pass filter. 12, these wires being connected both to the transmitting transformer 13 and to a receiving relay R. This relay functions during both receiving and transmitting, its purpose, in each case, being to determine the end of each pulse. It is a polarized relay with its contacts a, b normally held towards the left. In response to the first impulse of a code, in either direction, relay R reverses and completes a circuit for relay L1 which picks up and energizes relay L2. This relay then energizes relays LP and LB. The operation of relay L2 breaks the operating circuit of relay L1 and makes its energization dependent on relay R being in its normal, i.e. left-hand, position while relay L2 is only energized when relay R is reversed. Relays L1, L2 remain energized during the intervals constituting short code elements, but one or other,releases during the pause constituting a long element so that they serve to indicate, code character. A fresh code can only be initiated when relays L1, L2 are both released and consequently successive codes are necessarily spaced by an interval considerably longer than the interval between successive impulses. Contact b of relay R controls the counting relays 1 to 8 and 16 and also controls a pair of discriminating relays KS1, KS2, in the following manner. When relay R reverses, in response to the first impulse of the code, the energization of L1 completes a circuit through the upper winding of relay KS1 and counting relay 1, the direction of winding of KS1 being such as to hold its contacts normal. If the first element is short, relay KS1 remains normal, as shown, when relay R is returned to normal by the second impulse but, if the first element is long, relay L1 has time to release before the second impulse is received and contact L1b alters the circuit to pass through the lower winding of relay KS and this is such as to cause the contacts of relay KS1 to move over to the right. In response to the second impulse, relay R closes a circuit over contacts LBe and L2b through relay KS2 and contacts 8a and 1b to operate counting relay 2. This circuit also energizes relay KS2 in the normal direction, -as shown, but if the second impulse is long, relay L2 releases before the third impulse is received and relay KS2 is reversed. Counting relays 3 to 8 then operate in sequence, but the actual manner in which this is done depends on whether the station is transmitting or receiving and is described in greater detail late. In each case relay KS1 or KS2 is left normal for a short element and reversed for a long element. After relay 8 has picked up, a circuit is completed over contact 8c to operate a chain repeating relay CR, whereupon the counting relays run over a second cycle of operations to count the full sixteen impulses of the code, but at the end of this cycle relay 16 operates instead of relay 8. Transmitting (Central Office). The method of transmitting a signal consists of setting the signal (SW, S1G, &c.) as desired in a switchboard appropriate to the desired station (only station 1 is shown) and then pressing the appropriate push-button (e.g. 1PB) to initiate transmission. As described previously, the timing relays . L1, L2, LP, LB operate and release in sequence each time the relay R is operated by a pulse of the code. As soon as a push-button (e.g. 1PB) is pressed, a certain combination of relays P, according to the desired station, is operated over circuits running from wire 17, connected to battery at contact L2c, to wire 15 connected to earth at relay ST. This energizes the starting relay ST and connects battery to wire 28, so as'to energize relay M, which thereupon energizes the impulse transformer 13 and connects it to line. This impulse is, however, in such a direction that. all line relays R are operated in the normal direction, i.e. contacts a and b move to the left. The impulse is not part of the code. Immediately relay M picks up, relay T becomes energized and delivers the first impulse of the code to line, thereby reversing all line relays R, each of which operates its timing relays and first counting relay as described previously. The elements characteristic of the called station are 'then transmitted in order. If a short element is to be sent, the circuit for the appropriate counting relay is completed immediately through one of wires 22 to 27 and contact Pb and, as soon as the counting relay operates, its contact d shunts relay T to cause a pulse to pass to line. If the element is to be a long one then the circuit for the counting relay is not completed until after relay L1 (or L2) has released and consequently the pulse is delayed. The advance along the counting chain is controlled by the operation of relay R as described previously. The signal indication is sent in the second half of the message during which time relay CR is operated. Contacts CRc and CRd are then closed to allow the counting relays to operate in sequence without any delay in their operating circuits, but contact CRb is moved over so that the shunting circuits for relay T include contacts e of the counting relays, contacts b to i of relay O1S, this having been selected and energized by relays P, and contacts of the signal switches. It is possible, by using a relay CS (not shown) for several codes to be set up and stored and they are then transmitted in order. Receiving (Central Office). Relay R responds to receive impulses and actuates contact b to energize in turn relays KS and KS2 together with the counting relays in sequence. The first two counting relays always operate, these elements being used to determine the relative priority of messages, but relays 3 to 6 are used for the control station code and energizing circuits for them are made available by the appropriate combination of connections provided over the b contacts of relays P3 to P6. Long impulses allow relays L1 or L2 to release and so set up circuits over wires 62 to 67 to operate relays P in a combination characteristic of the calling station. This results in the selection of the appropriate station relay S, the relay 01S for station 1 being the only one shown, and the subsequent operation of relay D. The second cycle of operation of the counting relays is employed for the signal indication and, during this, contacts f of the counting relays extend circuits to polarized indication relays NWK, RWK, &c. which cause dighting of signal lamps, the direction of their operation being determined by polechanging contacts a, c of relays KS1; KS2 according to the nature of the element. Controlled stations equipment. The equipment at controlled stations is very similar to that at the control office, but as each equipment has only to respond to signals from the centra office it is reduced to a slightly more simplified form as shown in Figs. 2A and 2B. There are no P relays in the station but, instead, the wires 22 to 26 are permanently connected to wires 56, 57, 58 or 59 according to the station, so that unless the call code from the central office is correct for a given station, circuits cannot be completed for its counting relays after the second and consequently the station cannot respond. If the call signal is correct for the station under consideration then in the second cycle of operation of the counting relays their contacts f, in the manner described for the central office, complete circuits for functional relays WS, LHS, &c. Thus relay LHS, at contact a completes a circuit for relay LHR, and this, at contact c completes a circuit to operate the signal LH. At the same time contacts b and d of relay LHR set up circuits so that a signal indicative of the functions carried out is immediately sent back to the central office. During the transmission of this signal, the setting up of the station code in the first part of the message is controlled by the set connections between wires 31 to 37 and wires 60; 61, 70 and 71. Fig. 2c (not shown) is intended to replace Fig. 2B at a station where the number of controlled devices exceeds the capacity of a single normal station. In this case, one or more relays P, fulfilling the functions of these in Fig. 1B, are necessary in order to discriminate between the various signals, each relay P providing, in effect, the addition of another controlled station although only one set of counting and timing relays is employed. If any station commences transmitting and its relay R is operated by a received impulse, the holding circuit for relay M is broken at contact Rb and transmission ceases. This enables the line to be occupied by different stations in accordance with the relative superiority of their code calls, a short element taking precedence over a long element in each instance. Specifications 415,787 and 473,310 are referred to.