Abstract: A technique for measuring the insulation resistance of an insulated rail joint in the presence of leakage ground resistance (ballast resistance), as well as other track run-around paths, without the use of calibrated meters, such technique characterized by the use of a bridge circuit which includes a leg having the insulated joint therein whose resistance is being measured, the other three legs including a resistor of fixed known value and two variable resistors respectively, such that when the variable resistors are varied to obtain simultaneously both (a) the null of the rail, or ballast, current, and (b) ballast in the bridge circuit, the resistance value of the insulated joint is determined.

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: A vital communication system connects an input location to an output location using a non-vital communication link. In addition to transmitting, from the input location to the output location, a word with a bit dedicated to each different input, a system check word is transmitted. Each different input is assigned a unique multi-bit value, and the system check word comprises a linear combination of the unique multi-bit values for each of the inputs in a given binary state. Thus, there is a relationship between the transmitted words with bits dedicated to each input line and the system check word. At the output location, this correspondence is checked for. In addition, a further check is employed which first produces an output check word made up of a linear combination of the unique names for each output which are not in the given binary state. This output check word is then linearly combined with the received system check word.

Abstract: A polarity sensitive relay fabricated of and controlled by, solid state components is provided to produce a more trouble-free and smaller device. The relay may be made in first and second versions, the first of which responds to input signals of a single polarity and the second of which produces first and second output signals in response to input signals of first and second polarities, respectively. The relays include first or second Wiegand modules each of which has a drive coil, an input signal coil and an output signal winding. The Wiegand modules are placed in a steady state magnetic bias and the drive coils pulsed at a predetermined frequency. When two modules are used, the input signal coils are connected in series and in a manner to produce opposite magnetic effects on their associated Wiegand modules.

Abstract: An improved signal light employing a deep-dish reflector and critically positioned mask or masks for blocking at least some selected light rays having their origin in an external source to reduce, or eliminate, phantom signals. The mask is effective to block out at least a portion of the reflector which reflects light, from an external source, back out of the signal in a direction parallel to the reflector axis. The mask may take the form of a planar ring, a cylindrical surface, a cone or portions thereof. Other shapes may prove expedient or the reflector may be treated in selected and controlled locations to inhibit reflection. The mask may comprise any suitable material such as an opaque material or an electrically controlled optical shutter which is closed when it is desired to inhibit phantom signals and opened to accommodate normal signals.

Abstract: An alarm or signalling system between a transmitter station and a receiver station either or both of which may be in motion. A signal is selectively radiated from the transmitter station for detection at the receiver station. The receiver station includes processing means for responding to the received signal and producing a new signal indicative of selected physical relationships between the transmitter and receiver stations during the period of signal transmission and reception. The modified signal may indicate approaching or departing relative motion and/or magnitude of separation. One embodiment may incorporate synchronizing signals transmitted from a central control station. This embodiment may include receiver stations with and without the synchronizing equipment.

Abstract: Apparatus for insuring a vehicle operator's attentiveness at potentially dangerous locations along a path of travel. A signalling device is provided in advance of a potentially dangerous location, in the direction of travel of the vehicle. A vehicle carried signal responsive device responds to the signalling device when within the effective zone of the signalling device. The vehicle includes warning apparatus, for example, an alarm and a buzzer. The vehicle also includes an operator actuatable push button and a speed sensing apparatus. A control device responds to the push button and to the vehicle carried signal responsive device to operate either the buzzer or the alarm. If the operator evidences his alertness to the potentially dangerous location by actuating the push button prior to reaching the signalling device (within some constraint), the control apparatus merely sounds the buzzer when the signalling device is detected and resets itself.

Abstract: A microprocessor based vital delay circuit is provided which is arranged to emit an output no less than a predetermined time after an input stimulus. The predetermined time, which corresponds to the delay, is controlled by selecting the relationship between two quantities. A digital processor performs a series of computations on the two quantities, each computation is arranged to take unit time and by selecting the proper relationship between the two quantities, the total series of computations takes a predetermined amount of time. Before the output is allowed to occur, several checks are performed to insure that no hardware or software failures have erroneously generated the result. One novel checking technique insures that the clock frequency has not changed, and this technique is applicable to a wide variety of devices in which digital techniques are employed.

Abstract: A control system including apparatus for the transmission of information for the control of vehicles travelling in one direction on a guideway. The guideway is broken down into a plurality of groups of uniquely identified sequential blocks. Each block has at least one vehicle detector for detecting the presence of a vehicle and having an operated condition responsive to vehicle detection. Each block further includes a transmitter for providing, to a vehicle within the block, information concerning the block it is in as well as information regarding the identity of the next downstream occupied or unavailable block. To this end, each block has associated with it a word generator for producing a signal identifying the block; the word generator is coupled to the block transmitter, which transmitter is only enabled when the vehicle detector is in its operated condition.

Abstract: A fail-safe time delay circuit is provided to produce an output a predetermined time, and no less than a predetermined time after an input stimulus. The circuit includes a driving circuit for a pair of relays which are operated at slightly greater than 50% duty cycle and out of phase such that, except when the circuit is de-energized, at least one of the relays is always energized. The contacts of the two relays are employed in a balanced voltage amplifier to produce a bi-polar signal, with the magnitude of both polarities increasing, with the time required for the increase to a defined threshold establishing the time delay. A pair of threshold circuits are coupled to the output of the balanced voltage amplifier such that each threshold circuit (one responding to the positive portion, and the other the negative portion of the bi-polar output) is energized when the respective portion of the bi-polar signal is detected to reach the associated threshold.

Abstract: A highway crossing warning system includes a motion detector transmitter and receiver respectively coupled to the track rails adjacent the highway crossing for detecting motion of an approaching train. Wrap-around approach sections initiate operation of the highway crossing warning, but once motion is detected, the motion detector can serve to inhibit the highway crossing warning, after a predetermined delay, if motion indication ceases. To increase the effectiveness of the motion detection, the motion detector transmitter impresses a modulated carrier onto the track rails, wherein the modulation is phase locked to the carrier. The receiver, tuned to the carrier frequency, detects the modulation, and then determines from the level of demodulated signal whether or not approaching motion is detected. The transmitter employs solid state circuits switched between saturated and off conditions to prevent circuit component failures from masking approach motion.

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 control system for a plurality of vehicles provides for efficient communication while minimizing necessary bandwidth and communication delays. Periodic reports are received from the vehicles by a controlling authority. All vehicles in motion continually receive a permissive GO signal. When the controlling authority determines a vehicle should be stopped, it immediately addresses a STOP command thereto. The addressed vehicle acknowledges the message. Failure of the controlling authority to receive the acknowledgement results in removal of the permissive GO, stopping all vehicles.

Abstract: A vehicle control system monitors vehicle passage at predetermined locations. Each time a vehicle passes a predetermined location a window is created for passage of that vehicle at the next predetermined location. So long as the vehicle actually passes the next location during the window the vehicle is allowed to continue its travel. As a further check each location ensures that safe separation is maintained between vehicles by allowing continued travel only if a minimum time separation is maintained. The system also responds to coupled vehicles by detecting that the time separation is below a predetermined value indicative of coupled vehicles and thus minimum time separation need not be enforced. In one embodiment, passage of a vehicle outside of a time window results in immediate protective action such as by de-energizing the power to each of the vehicles in the system to prevent violation of minimum safe separation rules.

Abstract: The control system operates vehicles over a right-of-way divided into a plurality of zones and selects the direction of traffic along the right-of-way. The presence of a vehicle is sensed when it enters the zone from either direction and the occupancy of the zone is registered. The occupancy registration is indicated by a magnetically actuated switch to operatively control restrictive aspects in accordance with selected number of zones behind the leading vehicle relative to the selected direction of traffic.