Abstract: An apparatus and method for supplying cab signal to a rail vehicle on a section of track composed of sequentially adjacent railway track circuit blocks. Respective receivers of each track circuit block are monitored for the presence of a vehicle within that block. The cab signal apparatus is controlled to transmit a signal to a block when the output from the respective receiver in that block indicates a different condition from the adjacent receiver of an adjacent block. Output voltages from adjacent receivers are compared to enable transmission of a cab signal. Comparison of adjacent receiver outputs is accomplished through use of a diode bridge.

Abstract: An audio frequency (AF) track circuit whereby a railway track tuned loop transmitter operating in a dual resonant mode, for handling, two signal frequencies, can be coupled to the rails. Each frequency is conducted through a tuning unit having series and parallel branches tuned to each frequency. The track circuit using the tuned loop transmitter eliminates DC return current imbalance effects while maintaining suitably high track circuit shunting sensitivity.

Abstract: A railway system including a track and a train adapted to run on the track. A power feed line comprising a series of feed sections is provided to extend along the track. A plurality of stations are provided along the track and the station has a power supply unit adapted to be selectively connected with one of the feed sections to supply a controlled three-phase AC power to the feed section to thereby operate the train on that feed section in a desired mode. The train has a pair of collecting shoes which are connected with the tracting motor in parallel with each other and arranged with a space in a longitudinal direction of the train. In the station, there is an insulated junction between the two adjacent feed sections which is located so that it is between the two collecting shoes on the train which is stopped in the station at a predetermined position.

Abstract: Broken rail detection in a block of track without the need or expense of conventional signalling uses a chain of transmitters and receivers connected to the rails and defining sections of the block between the ends of the block. Either cyclically at a predetermined code rate or upon command of an external unit; an alternating current (AC) signal is launched from one end of the block and is repeated at different frequencies in each of the sections. When received at the end of the block, an indication of the absence of a broken rail condition is given either (a) by way of pole line or radio communication to a central control or dispatcher point and thence back to the trains, or (b) signals at the ends of the block are flashed at the code rate. The detected signal at the code rate may be used to modulate a direct current which is transmitted along the rails in the block to a signal at the opposite end of the block which also flashes at the code rate to indicate a safe condition.

Abstract: An improved audio frequency track circuit system utilizes a synchronous train detection arrangement and reduces the number of fixed code rate modulated carrier signals. As few as two carrier signals are alternately applied at discrete points along a pair of jointless track rails to define the transmitter ends of the track sections, with complementary receivers defining the opposite ends. The two carrier signals are coded at one of two phase angles which are 90.degree. out-of-phase so that, when assigned, the nearest possible interfering signal is 90.degree. out-of-phase and is rejected thereby. Like carrier frequency transmitter/receiver arrangements are disposed on opposite sides of an insulated joint but are coded 180.degree. out-of-phase so that a breakdown of the insulated joint is detected and the false code signal is rejected.

Abstract: A railway track circuit arrangement particularly suitable for the short track circuit, down to approximately 40 metres, required in metro transit systems. Based on conventional A.C. track signalling principles for continuous track rails, the boundaries between adjacent track sections are defined by electric separation zones. An electrical short is connected between the running rails and an A.C. signal tuning unit is connected approximately 6 metres away to tune the end loop thus formed to resonance at the selected track signal frequency. The tuning units comprise a capacitor, the value of which is selected for resonance tuning, and a transformer a winding of which is connected in series with the capacitor, and a track circuit signal transmitter or receiver is connected through a second winding of the transformer. In order to reduce mutual coupling between track circuits by longitudinal leakage, in each joint, two electrical short may be connected between the rails spaced apart approximately 0.75 metre.

Abstract: A bridge network 1 of current switching devices 2, 3, 4, 5 is operated in full wave manner by controlling signals A, B, C, D respectively produced by two similar, parallel and pulse width modulated power control circuits 12, 13 connected to receive a common input signal, one pair of opposing switch devices (2, 5) being controlled by one circuit 12 and the other pair 3, 4 being controlled by the other circuit 13. The pulse width control inputs 14 of the circuits 12, 13 are connected to voltage sensing means in the bridge supply circuit so that the pulse width of the control signals A, B, C, D is determined in accordance with the bridge supply level. The arrangement is such that the control circuits 12, 13 although not be designed to fail-to-safety standards operate in a fail-safe manner to provide a constant level output of the input signal.

Abstract: A sensor arrangement is disclosed for detecting the presence of an axle of a rail vehicle in a short length of a track. The arrangement includes a bridge coupled to and including resistances of the rail upon which the vehicle travels. This bridge is unbalanced by wheels of an axle shunting resistance of the bridge with the bridge unbalance producing an output indicative of the presence of the axle. Two such arrangements displaced relative to each other will enable detecting the direction of movement of the vehicle. This sensor arrangement contains no electric components on the rail and is insensitive to interference from rail currents and electromagnetic rail brakes.

Abstract: An improvement in apparatus for the secure transmission of information through rails in zones of propagation independent from the sections of the track block-section system embodying the use of series resonant circuits tuned to the information carrier frequency and connected between the rails at the end of a transmission zone and comprising two identical series resonant circuits disposed in parallel and each comprising a capacitor in series with the primary winding of a transformer, with the secondary windings of the two transformers being connected in series and in opposition, so that an oscillating signal appears at the terminals of the circuit thus formed in the case of failure of one of the resonant circuits.

Abstract: A system for transmitting data long rails of a railway track for reception by a receiver mounted on a vehicle of the train. The system includes resonance circuits defining contiguous zones which are independent of a block system of the railway track. An insulative conductive loop is placed between the rails of the track and proximate the resonance circuits. An AC generator and modulation are provided to produce a modulated carrier frequency corresponding to the data to be transmitted and is coupled to the conductive loop. The receiver is positioned at the front of the train when the conductive loop is positioned near the downstream side of each zone and toward the rear of the train when the conductive loop is positioned toward the upstream side of each zone relative to the direction of train travel.

Abstract: A railroad signal circuit includes a transmitter and a receiver which have a common connection to the track rails at one end of a signal block. There will be a similar transmitter and receiver at the opposite end of the signal block. A transmit/receive switch is connected in circuit with the transmitter and there is a code following element connecting the receiver to the transmit/receive switch and transmitter. The code following element comprises a Hall effect cell whose output is connected to the receiver.

Abstract: A tuned transformer element has its primary winding coupled, in series with a fuse of preselected rating, to the rails of the track circuit. A secondary winding supplies input energy to the track circuit receiver unit which detects occupancy conditions of the track section. A third winding is capacitor tuned to resonate with the primary winding at the track circuit frequency. Thus the transformer appears as a parallel resonant load of high impedance in multiple with the track receiver which then operates normally. At propulsion frequency, the impedance of the primary is small while the parallel capacitive reactance is large, so that the parallel network gives the transformer unit a low impedance at this frequency.

Abstract: A track circuit is disclosed and includes rails which are fed from a main signal transmitter and which rails, at an information point a required distance from the transmitter, are shunted by a cross impedance, with which impedance, with respect to the track of the main signal, an additional transmitter of an auxiliary signal and a main receiver for receiving signals from the main and additional transmitter are serially connected. A signal indicating a free track is obtained if the main receiver is energized.

Abstract: A decoupling arrangement for non-insulated track circuits is disclosed wherein the receiving circuit of the evaluating unit for the AC track currents is electrically separated from the traction-current-carrying parts of the track. The cross bonds between the two rails of a track may be shorting bonds or so-called S bonds. The arrangement according to the invention improves the tuning behavior of the track circuit receivers considerably.

Abstract: A railroad signal system includes an A type transmitter and receiver for sending and receiving signal messages in one direction and a B type transmitter and receiver for sending and receiving signal messages in the opposite direction. The A transmitter and the B receiver are located at one end of a signal block and the B transmitter and A receiver are located at the opposite end. The A transmitter provides an A type DC message and the B transmitter provides a B type DC message. The A receiver is responsive to only an A type message and the B receiver is responsive to only a B type message.

Abstract: A train approach detector uses frequencies in the audio spectrum to activate grade crossing protection devices in advance of and during the presence of railroad trains at grade crossings. The detector is completely solid state, and includes one transmitter and one receiver each connected to the tracks so that transmitted and received track signals, which are partially pulse modulated for optimum filtering and signal coupling and minimum third harmonic radiation, appear on opposite sides of the crossing. The section of track between the transmitter and receiver is designated as a crossing island and sections of rail outside of the island are known as approaches.

Abstract: An arrangement enabling continuous control of vehicles on a track divided into individual areas comprises at least one track-conductor loop associated with the track in each of the areas having N transpositions therein, where N is an integer greater than two, the loop communicating data between the vehicles and a fixed control station by being coupled at opposite ends thereof to a different one of two supply units coupled to the control station and by being inductively coupled to communicating equipment on the vehicles. The one loop further comprises coupling elements disposed intermediate adjacent ones of the N transpositions to subdivide the loop into N track-conductor loops.

Abstract: An audio frequency track circuit with improved security in the train detection function for rapid transit applications for use with uninsulated rails includes an improved transmitter and receiver. The transmitter modulates a track frequency carrier with a fixed code rate, regardless of the code rate employed to modulate the train information frequency. The receiver includes a decoder tuned to the track frequency modulation rate. By using such a sharply tuned decoder, the noise protection threshold is increased. Because of its application to uninsulated rails, with the associated lack of hard track circuit boundaries, adjacent track circuits have different track frequency modulation rates to insure that the modulated track frequency signal, from one track circuit, is not effective to operate a track relay in another circuit even under failure conditions.

Abstract: A railroad highway crossing warning system including pickup coils for sensing current flowing in the track rails of an approach zone, a circuit for sensing the voltage across the track rails, band-pass filter circuits for filtering the voltage and current derived from the track rails, impedance calculator circuits for calculating the track impedance, phase detector circuits for detecting the phase angle between the voltage and current, a multiplier circuit for linearizing the track impedance by multiplying the track impedance by a function of the phase angle, a data sampler circuit for sampling the linearized track impedance at given periodic intervals, a motion detector and crossing predictor circuit for detecting the motion of a train and for predicting the time of arrival at the crossing by comparing the predicted time of arrival with an advanced warning time, and a logic gate circuit for activating the warning apparatus at the crossing when the predicted time of arrival is less than the advanced warning t

Abstract: An electronic system which emulates the operation of a polar relay for applying coded pulses to railway tracks has separate signaling circuits having signaling devices responsive to a separate inputs which provide operating power to the circuits. The circuits are interlocked by connecting the inputs to the signaling devices in inverse relationship. One input excludes the other. The signaling devices may be light emitting isolators with switching transistors which control the application of current pulses through the rails of the track while isolating the track battery which supplies the current for these pulses from the local battery which provides the inputs to the signaling circuits. The signaling circuits establish current paths through the light emitting signaling devices at predetermined times after the inputs are applied to emulate the pickup and drop away time of the polar relay.

Abstract: A self-powered receiver including a series resonant circuit tuned to the carrier frequency of a modulated carrier signal. A demodulator for detecting the envelope which switches a switching transistor ON during the mark portions of the modulator carrier signals and switches the switching transistor OFF during the space portions. A parallel resonant circuit is driven by the switching transistor to produce a.c. modulations to be coupled to a full-wave rectifier. The rectified voltage of the rectifier is used to energize an electromagnetic relay.

Abstract: A highway crossing warning system for monitoring the motion and predicting the time of arrival of an approaching train at the highway crossing and for detecting the presence of a broken rail in the approach zone by feeding dual frequency signals into the track rails and measuring the track impedances at the two frequencies and the phase angle of the lower of the two frequencies.

Abstract: An electrical joint for separating adjacent block circuits of a railway signaling system in which the rails of the railway track serve as conductors. The upstream circuit block carries first frequency signals and the downstream block circuit carries second frequency signals. The electrical block separating joints are bounded by tuning units of which one may be a mere impedance and which are responsive to the frequencies of the circuit blocks and constitute respectively a low impedance for the first or second frequency and a capacitive impedance for the other of the first or second frequency. There are transmitter and receiver units the latter of which is associated to activate a control device, e.g. a relay, for the associated block circuit to de-activate the control device when a vehicle enters the electrical joint by a shunting effect.

Abstract: A continuity monitor and indicator circuit for monitoring the continuity of a segment of a pair of control conductors along which a control current flows includes capacitors at each end of the segment being monitored, which capacitors are connected to bridge the conductors and provide an a.c. electrical path between the conductors. A transformer has its secondary winding connected in series with one of the control conductors in the segment and an oscillator is connected to the primary winding of the transformer. The oscillator arrangement is such that it will provide an output signal when the closed a.c. electrical loop formed by the secondary winding of the transformer, the control conductor segment, and the bridging capacitors is broken. A detector is responsive to the oscillator output to detect such output and supply a detector output to a delay means which, in turn, provides an alarm output after receipt of the detector output for a predetermined period of time.

Abstract: An electronic track zone detecting device for providing a signal representing location and direction of travel of a railway apparatus within the zone. The detecting device comprises two frames, of insulated open conductive loop structures, defining the extremities of the zone.

Abstract: There is disclosed a circuit for energizing a vital relay in response to an input signal that is modulated between two frequencies. A discriminator circuit responds to the modulated frequencies and alternately produces an output patented of one polarity and then a reverse polarity in response to the modulated signals. Coupled between the discriminator and the vital relay is a relay driver which responds to the output of the discriminator and energizes the vital relay. A d.c. power supply is coupled to the relay driver. The vital relay includes two windings. Failure of the modulation, the d.c. source or virtually any circuit element, will result in release of the vital relay. The disclosed embodiment uses photoresistors as switching elements.

Abstract: A system for protecting data communication against disturbances caused by unsymmetrical standing waves along track conductors wherein automatically controlled terminating resistors are utilized to prevent the formation of standing waves either totally or nearly totally. Baluns may be utilized to cause such standing waves to be automatically balanced. The sensitivity of continuous automatic train control to atmospheric influences and conductor asymmetries is eliminated in accordance with the invention.

Abstract: First and second monitoring channel apparatus detect the level of the normal output and load current, respectively, supplied by a principal energy source to a variable load network. Source output varies from normal to low level and load current from low to high level as load network varies between relatively no load and heavy load conditions. The monitor channel detection signals are checked through a logic circuit so that if at least one exceeds a predetermined level indicating the operable condition of the principal source, a registry device is actuated to hold the energy supply leads to the load network connected to the principal source. If neither monitor detects an operable condition of the source, the registry device is operated to activate, and transfer the load energy supply leads to, a standby source.

Abstract: A track circuit signalling system for an electrified rapid transit system using significantly fewer components is provided. Instead of a transmitter and receiver at each track circuit boundary, alternate boundaries have transmitters only; and the intermediate boundaries have two receivers. The coupling units for the two receivers are more economical than the prior art coupling unit for coupling the transmitter-receiver combination. The transmitters on each side of a receiver pair transmit signals on different carrier frequencies. Each transmitter transmits in both directions from its location. Of the two receivers at a given boundary, one is tuned to respond to signals from the transmitter on one side, while the other receiver of the pair is tuned to respond to signals from the transmitter on the other side. For special applications using overlapping track circuits, selected transmitters may be omitted and a single receiver used on each side of the omitted transmitter.

Abstract: An overlay selective harmonic transducer device is installed on affected track circuits, that is, track circuits on which interference with normal functioning has occurred due to traction power harmonics.

Abstract: A first transmitter-receiver movement detector system operable at a first frequency detects a train approaching a first grade crossing or other track location in response to train approach speed and distance, and a repeater receiver movement detector device also operable at such first frequency but located at a subsequent grade crossing or location, which is relatively proximate the first, is capable of looking through the first crossing even under unfavorable ballast conditions thereat to detect an approaching train with respect to its speed and distance from the second crossing. The output of the repeater receiver and that of a further transmitter-receiver movement detector system operable at a different frequency from the first are combined in a logic circuit to provide safe, minimum signal down time at the subsequent location.

Abstract: A detective circuit for railway points composed of three track sections connected together at a junction or for a railway crossing composed of four track sections connected together at a junction.

Abstract: There is described a track circuit for use with a track section which may or may not include a switch. The system detects the presence of a railroad vehicle within the track section as it constitutes a shunt across the track. The track section is divided into a plurality of segments with each segment having a common boundary with at least one other segment. Alternating current signals are induced into each track segment and a sensor is provided for sensing and responding to the induced a.c. signals. A modulator is provided for intermittently affecting the sensed signal and a detector is provided for detecting and responding to the changing signal.The detected signals are gated through a logic circuit which provides first and second outputs indicating: the changes are as might be anticipated as a result of the modulation introduced; or, the changes are other than might be anticipated as a result of the modulation, respectively.

Abstract: An antenna apparatus is disclosed for coupling audio frequency signals in relation to one or more vehicle track rails of a transit system for the purpose of determining vehicle occupancy of a given signal block and providing speed coded control signals to a vehicle moving along the track rail in that given signal block. It is desired that each signal block in the transit system track circuit operate with the signal level above a predetermined minimum signal level for reasons of vehicle occupational detection. The antenna apparatus is operative to enable desired adjustment of the signal level in a given signal block and in adjacent signal blocks relative to that given signal block.

Abstract: This invention covers train cab signal equipment for receiving frequency modulated rail code signals which, when decoded, provide a zone speed control signal which the railway train traversing the track rail must obey in order to proceed at a safe speed. The invention includes a signal limiter circuit which prevents the signal supplied to the several code frequency responsive networks in the decoder unit from exceeding a predetermined maximum value in order to assure a welldefined frequency bandwidth to which respective code filters in the frequency responsive networks are sensitive, so that only a single network is responsive to any given code signal. In addition, the limiter circuit supplies the respective frequency responsive networks with a code signal whose amplitude is proportional to rail current so long as the code signal is below the maximum level set by the limiter.

Abstract: An apparatus for detecting an approaching train within a track section utilizes a transmitter coupled to the rails at a feed point for applying a current to the track section. There is a receiver coupled to the track section for producing a signal representative of the impedance of the track section. There are devices for utilizing the received signal for detecting train motion, abnormally low impedance and abnormally high impedance of the track section. A normalizer circuit is connected to the receiver for increasing or decreasing the received signal gain within predetermined limits in accordance with variation in impedance of the track section.

Abstract: In a railroad interlocking, a cab signal transmitter is coupled to the rails at each exit location and at such other locations as are necessary to supply continuous cab signal energy to trains traversing any possible route through the interlocking. Where train shunts prevent the reception of cab signal energy, wire loops laid adjacent the rails carry the cab signal energy for train pickup. Each rail coupled transmitter is finally activated to supply energy when a train occupies an associated track section. However, the control circuit network for each transmitter also checks, as pertinent for the established route, that a route has been established and the approaching train authorized to traverse that route, that any succeeding track sections along the route are unoccupied, that the transmitter for a preceding section has been activated, and that transmitters for opposing or conflicting routes are not active.