Abstract: An alternating current code, alternately transmitted in each direction through the rails of a railroad track section, includes a selected number of pulses of alternately positive and negative polarity similar to a bi-polar DC code. Data is transmitted by pulse length, with long and short pulses representing binary digits 1 and 0, respectively. The code pattern, polarity and pulse length, is balanced to eliminate code distortion by track energy storage. The code pattern transmitted is determined, and received pulses are decoded, by a microprocessor with associated memory (PROM) which processes local input and output data. The processor also checks the operation of the associated apparatus, including input and output circuit and hardware integrity through monitor devices and feedback signals. A unique check signal output is produced only when the various monitor networks determine all operation is proper and that the various elements are free of faults.

Abstract: Reversal of the established traffic direction is initiated by a request for an entering train movement at the existing exit end of the single track stretch. This deenergizes the adjacent traffic line circuit section in the new direction. Line circuit deenergization cascades section by section through the stretch to the other end. At each location, the active traffic direction register relay is deenergized but the magnetic stick traffic relay holds in its established traffic position. At the new exit end, reception of the deenergization signal reverses positions of the traffic and direction register relays if the new approach track circuit is clear. This initiates the transmission of line circuit energy in the opposite direction. At each intermediate location, reception of this opposite direction line energy energizes the other direction register relay if the approach track circuit is clear.

Abstract: An electropneumatic door control for vehicles is disclosed which consists of a pneumatic portion and an electronic portion. The electronic portion processes successive commands actuated by the vehicle operator to channel the signals to the pneumatic portion of the apparatus to activate alternate door openings and closings. Any blockage of the door movement is detected and signals processed to reverse the door closing or to halt the opening until the fault is corrected. The electronic portion also assures that the vehicle doors can only be opened after the vehicle has come to a stop, that when the vehicle doors are open the station or parking brake is held engaged, and that an audible warning signal sounds for a predetermined interval before the closing of the door.

Abstract: This vital solid state relay incorporates only passive elements and is intended for use as a replacement for a two element AC track relay in AC track circuits. The local input signal is applied to a transformer whose secondary output, across a Zener diode, is a pulsed, square wave DC with regulated peak. The track input is applied through a noise rejection filter, tuned to track circuit frequency, to a coupling transformer. A series loop registry circuit includes the secondary of each transformer, a DC relay, and a varistor element. The sum of the transformer output signals, due to the Zener diode rectification, has a DC component. When local and track signals are both present and substantially in phase, the varistor switches to its high current condition to pick up the DC relay to indicate an unoccupied track section. Absence of the track input, out of phase conditions, or unmatched frequencies retains the varistor in its low current state and the DC relay releases to register an occupied section.

Abstract: A valve plate, inserted between the cylinder body and head parts of a compressor, holds the usual compression valve, which opens to connect the compression and pressure chambers during the compression stroke of the piston, and the suction valve which opens to connect the suction and compression chambers during the piston intake stroke. A separate plate-type idle valve also within the plate is positioned to open into a recess of the compression chamber so that there is no interference with the movement of the piston. The idle valve is controlled by an idle piston actuated by pressurized air admitted through a pressure regulator which opens when the reservoir pressure exceeds a predetermined level. Opening the idle valve shifts the compressor operation from compression to idle condition by permitting unhindered passage of air between suction and compression chambers.

Abstract: Vital transmission checking apparatus is disclosed for a communication channel which transmits quasi-static signals representing several alternative states of a function, e.g., the control function for a signal in a railway control system, one of which states is potentially unsafe. Each function channel transmits a digital signature code of predetermined length which is continuously repeated in a selected form, e.g., non-inverted, inverted, or alternately inverted and non-inverted, to represent the different states of the function. To provide a check of proper transmission, the repeated signature code is periodically corrupted in accordance with a predetermined error pattern which is repeated at a lower repition frequency than the code. The channel receiver is so designed that its output can only be held in the selected state when both the signature code and the error pattern in the received signal are correct. If a fault is detected, the receiver output is shifted to the most safe state of the function.

Abstract: Pressurization of closing and opening chambers of a door operator is controlled by first and second magnet valves coupled to the source of air. These valves are alternately energized by a switching network, e.g., a flip-flop, when sequentially actuated to close and open the door. The second magnet valve is biased to its vent position but the first valve is operated to its vent position by air through a double check valve when the second magnet valve is energized. Emergency and choke valves are inserted in series in the air supply to the magnet valves and normally pass air without restriction. Operation of the emergency valve, e.g., door blocked, shuts off air from the magnet valves and diverts that air to inhibit all output from the switching network and, through the check valve in opposite position, to operate the first magnet valve to vent position. Door operation is halted in position.

Abstract: A piston and geared rack assembly are moved by pressurized air in opposite directions within a power cylinder housing as the vehicle operator registers door closing and opening commands in a solenoid valve. This lateral movement is converted to rotary movement by a pinion gear driven by the rack and coupled to turn a spindle shaft which drives the door. At full stroke during door closing, the power piston actuates a valve to charge the lower chamber of an auxiliary cylinder to move a lift piston rod, movable within the spindle shaft, to raise the closed door into a locked position. Upon a door-open command, the solenoid valve exhausts the charged cylinder chambers, admits air into the upper chamber of the auxiliary cylinder to move the lift piston and rod to lower and release the door, and slowly charges the associated opening chamber. This enables the delayed movement of the power piston and rack assembly in the opposite direction, reversing the rotation of the pinion and spindle shaft, to open the door.

Abstract: An elastomeric sleeve is inserted in the hole in the cock body which has multiple passages for the fluid. A plug, which may be positioned to connect selected passages, is placed within the sleeve in the hole. Either the contacting surfaces between the hole and sleeve or the rubbing surfaces between the sleeve and plug are tapered. A spring, seated on the base of the body or a plug flange, exerts upward pressure on the sleeve to assure tight contact between adjacent surfaces to eliminate fluid leaks.

Abstract: The two inputs of a first flip-flop (FF) are alternately energized over a pair of opposite contacts of a code transmitter. Outputs of a second FF alternately enable a pair of logic gates to pass first or second output pulses of the first FF as clock pulses which drive a counter which produces an output pulse after each preselected count X. Each counter output pulse, equal in length to a half cycle of the code, triggers the second FF to its opposite state. A magnetic stick code repeater relay is driven between its two positions by energy supplied from a normally active driver circuit over another pair of opposite contacts of the code transmitter. The driver circuit is optically coupled to be turned off during each counter output pulse, thus inhibiting repeater relay operation during the corresponding half code cycle. This relay holds in its existing position, blanking a half cycle code period, and then is held by the again active driver circuit during the subsequent half cycle.

Abstract: A pair of transistors, alternately activated by a low frequency generator, alternately connect the positive and negative terminals of the monitored DC source to the common bus of the ground detector apparatus. Each produces a fault current signal flow through any ground fault existing on the other source terminal, with the return circuit including a permanent ground rod, the input of a comparator, and apparatus common. An opposing reference current signal of preselected level is applied to the comparator input, at the same time as each fault signal, from a current pump network driven by the low frequency generator. If each reference current signal is larger than the corresponding fault current signal, the comparator output is a square wave signal of alternate plus and minus pulses which is applied to a negative voltage generator network controlled by contacts of two synchronizing relays alternately driven by the low frequency generator.

Abstract: Coded energy applied to the track circuit rails for cab signal control when a train occupies the section is also applied over a line circuit to the local input of the solid state track relay unit and to a code reset module in which it drives a code following relay and charges a timing capacitor during a predetermined number of code pulses. When the section becomes unoccupied, the track relay unit produces a coded output, from the combined rail and local inputs, to which the track registry relay is non-responsive. An analog storage circuit in the reset module receives and stores this coded output energy during each timing period. During each code off-time, the timing capacitor is connected to a switching relay circuit controlled by a DIAC unit.

Abstract: A separate relay is connected across the output of each speed command filter decoder in the train carried apparatus, except that decoder associated with the highest authorized speed. Each relay has special make-and-break contacts which cannot be simultaneously closed in normal operation. When the relay is energized by an output from the associated decoder, the normally open contacts close to apply that speed command to the corresponding input of the speed governor. The associated normally closed contacts open at the same time to remove operating energy from all higher speed decoders to inhibit simultaneous response from any cause. This action assures that the train is controlled by the lowest active speed command if more than one filter decoder inadvertently responds to produce simultaneous speed command outputs.

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: The speed proportional frequency signal from the speed generator being checked is amplified and applied to a highpass filter-rectifier with a low frequency limit corresponding to a predetermined minimum train speed. Polarity of the rectified output is opposite to the DC operating energy so that, with four-terminal load resistor and smoothing capacitor, the filter-rectifier operation is vital. The rectified signal activates an oscillator level detector when its level exceeds the breakdown of a Zener diode control device selected to correspond to minimum speed output. The level detector is coupled by a stepdown transformer to a differential amplifier biased by a signal supplied from an associated zero speed detector. The bias signal has sufficient level to enable the differential amplifier to produce an output in response to the level detector input only when the train speed is greater than zero.

Abstract: A compound check valve device comprising a housing having a pair of oppositely disposed inlet ports and an outlet port therebetween, a hollow, two-part valve carrier reciprocably operable in the housing between the inlet ports for selectively communicating the inlet ports, singly or concurrently, to the outlet port, and a spring disposed between the two parts of the valve carrier for biasing respective valves mounted on the valve carrier toward respective valve seats surrounding the two inlet ports so that, in the absence of pressure at the inlet ports, the valve carrier assumes a neutral position in which the inlet ports are cut off from the outlet port, and when pressure is supplied to the inlet ports, the valve carrier assumes a position according to the relative pressures at the inlet ports to communicate either both inlet ports or one inlet port to the outlet port.

Abstract: An LC series resonant regulator is connected across the output of the inverter circuit of a static converter apparatus to vary the output voltage level as the inverter operating frequency varies from a preselected frequency at which the regulator circuit is tuned. The load is coupled across the capacitor element of the regulator and a level detector coupled across the load input. This detector registers variations of the input to the load from a predetermined desired level of load voltage and supplies a feedback signal, indicative of any detected variations, to the control circuit for the inverter circuit element. This control circuit is responsive to a feedback signal to vary the operating frequency of the static inverter so that the regulator varies the output voltage applied to the load to restore the desired voltage level.

Abstract: A digital comparator with a comparison cell for each pair of digits of two words stored in separate register banks. Each corresponding pair of register stages is coupled to the associated comparator cell by a rectifier interface network which supplies an actuating signal only when the associated word digits have complementary characteristics. The comparator cells are coupled in series and interfaced to input and output by optical coupler units. Each cell includes an LC network tuned to the selected frequency of an input test signal which is passed through the comparator chain, from highest to lowest order cells, only if each cell is actuated by an input signal from the associated interface network, thus indicating that each pair of word digits is complementary.

Abstract: A holder molded of suitable elastomeric material cradles a plug-in relay in operating position, with access openings for calibration adjustments, visual inspection of contacts, and plug coupling of connecting leads. The holder is mounted to a mounting plate and/or the shelf by bolts inserted into cylindrical openings in the bottom of the holder and through a web or diaphragm molded as an integral part of the holder. A spacer tube placed over each bolt spaces the holder a selected distance above the mounting plate. Washer disks of the elastomeric material are placed on both sides of the diaphragm and a lock nut secured onto the bolt to fasten the holder in place. The diaphragms, disks, and spacers combine to provide vibration damping and shock isolation for the relay.

Abstract: Adjacent stations along a single track railroad without continuous train detection, are coupled by a communication channel over which distinctive signals requesting, acknowledging, accepting, and confirming completion of, train movements are transmitted. The operator at the departure station manually initiates the transmission of a first signal requesting a train movement to the adjacent station. The other station operator acknowledges the movement request by manually actuating the transmission of a second distinct signal accepting the move. The two signals jointly establish the requested traffic direction through the single track and clear the departure signal for the train. Occupancy of the single track by the train locks the channel to inhibit other movement requests, thus protecting the train while moving through the non-detection stretch. Arrival of the train at the far station is registered and confirmed by the operator who manually actuates the transmission of a train complete third signal.