Abstract: A semiconductor contact arrangement comprising a semiconductor wafer having on one of its major faces an area of one type of conductivity and an electrical contact in face-to-face engagement with that area, in which the contact is located with respect to that area and is secured to the sandwich by a stud welded to the wafer and projecting into a hole extending through the contact from the face thereof engaged with the wafer.

Abstract: There is disclosed a circuit arrangement including a load (7) and a current source (1) for supplying current to the load via a current path with a winding (3). A core of magnetizable material (2) is coupled inductively with the winding and a Hall effect transducer (4) detects magnetic flux in the core for use in producing an output indication dependant on the magnitude of the load current. For testing the correct functioning of circuit(s), the circuit arrangement is further provided with an additional winding (6) on the magnetizable core, through which a further current source supply a further current, in which the core is also inductively coupled so that the transducer also detects flux in the core due to the further current.

Abstract: Fast Fourier Transform methods of analyzing signal frequencies spectra yield results from zero frequencies upwards. Thus, when the frequency band of interest is not at very low frequencies a lot of wasted calculations may be performed, and resolution and computation time have to be traded-off against each other, often falling short of the requirements for both. A technique is described in which the signal to be analyzed is passed through an anti-alias filter and initial transform data is collected by undersampling. In a railway track circuit receiver which is to identify a predetermined carrier frequency or FSK signal, the anti-alias filter is selected to exclude frequencies other than those in a frequency band including the particular track signal so that there is no ambiguity in the calculated transform results.

Abstract: A railway vehicle control system particularly, but not exclusively, suitable for controlling single track working. Transponders are located at fixed positions along the track such as at intersections, points and so on, and a vehicle is provided with sensors for detecting the transponders. A central control office supplies information concerning an identifying characteristic of the next transponders expected to be detected, when this happens the event triggers apparatus on the vehicle to communicate with the central office which then supplies information to identify the next transponder. The same sequence of events ensues as each successive transponder is passed. The transponders may be staggered alternately to opposite sides of the track for identification purposes. If the expected transponder is not detected but instead a different transponder is encountered, then a vehicle safety function such as the emergency brakes, may be brought into operation.

Abstract: A spring applied force actuator having an output member movable from a first position to a second output position, a first power spring by which can be generated on the output member an output force when the member is in its second position, first power means by which potential energy can be generated in the first spring therein to be held until the spring is released to apply its stored force as an output force on the output member, a second spring release of potential energy stored in which moves the output member from its first position to its second output position, and second power means by which the output member can be moved back from its second output position to its first position thereby, at the same time, generating in the second spring the potential energy subsequently to move the output member back to its second output position upon the subsequent release of that second spring.

Abstract: An automatic vehicle protection system, e.g. for a railway vehicle, in which continuous contact is maintained with a train via transmissions carried by the normal track circuit signals. Information relayed to the train through these transmissions may concern speed limits, forward section occupancy and so on which can replace normal track side visual signalling systems as a means of controlling trains. It is, therefore of utmost importance to ensure that a train receives the correct transmission, which it is intended to receive, and not those meant for other trains. By arranging for track circuit signal freqencies in predetermined sequences and providing the train with means for determining whether or not the sequence of frequencies it encounters as it traverses a line the safety of the train, and the integrity of the system may be continuously proved.

Abstract: A railway vehicle control system comprises a railway track (1) and a plurality of transponders (N, N+1, N+2) at predetermined positions along the track. A railway vehicle (2) moves along the track, the vehicle having means (20, 21) for detecting each of the transponders. A control location has means (4, 5, 6, 7, 7a) for periodically transmitting vital safety signalling information to the vehicle via a radio link. In response to detection of one of the transponders, the vehicle sends a first message via the link to the control location and in response to reception of the first message by the control location, the vital safety signalling information is sent a first time from the control location to the vehicle via the link, then from the vehicle to the control location via the link and then a second time from the control location to the vehicle via the link.

Abstract: To ensure the safe operation of an electronic circuit, for example an amplitude modulated carrier signal generator, an output of the circuit is analyzed to prove the presence of predetermined signal characteristics, for example the carrier signal, or a modulation frequency. The predetermined signal alternatively may be superimposed on an input to the electronic signal and proved subsequently to be present in the output. The output of the circuit is passed inhibited, according to whether or not the signal characteristics are proved present, by means of an output enable gate which is self-latching providing the output continues to be proved correct. A start-up circuit delays a possible inhibit for a limited period following initial power connection to the circuit in order that the output can become established.

Abstract: An AND function gating circuit for A.C. signals comprising several magnetic circuits around a common limb, each circuit having a separate input winding and a single output winding on the common limb. The magnetic flux level in the common limb is greatly increased when all input windings are simultaneously energized by A.C. signals of the same frequency and in phase relative to the output achieved under other input signal conditions.

Abstract: Electrical circuit configurations are described for the operation of an electrically powered actuator in an emergency to drive the actuator to a predetermined position. In particular the actuator is connected to apply friction brakes of a railway vehicle. The configurations have in common are emergency power circuit connected between an emergency power source and the actuator, means for breaking the power circuit when the actuator reaches the emergency position and latching means to prevent run-back. Preferably and in order to minimize size and weight the emergency power source is of limited capacity, sufficient for, say, two such emergency applications and is recharged from a normal power supply; the recharging circuit being interlocked with the latching means such that the actuator may not be released from the emergency position unless the power source has sufficient charge for at least one further emergency operation.

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 semiconductor housing particularly useful for very high current devices, e.g. transistors and G.T.O. thyristors, in which a control lead to the base or gate of the device, which also has to carry a relatively high current, passes through an insulating wall of the housing. This control lead is enclosed within a tube which passes through an insulating wall of the housing and which is hermetically sealed to it, the tube is also hermetically sealed to the conductor at either end. The coefficient of expansion of the tube is chosen so as to be substantially the same as the coefficient of expansion of the material of the insulating wall, which may be made of ceramic material or the like. The arrangement avoids corrosion effects as a result of the entrapment of plating salts etc. which are known to adversely affect the assembly and especially the electrical performance of the control lead connection.

Abstract: A governing factor of the switching characteristics of a thyristor device is base layer resistivity, for example in a gate turn-off device, to maximize load current it is preferably low but, the reverse breakdown voltage of the emitter-base junction is improved if the resistivity is high. The invention proposes a modified base layer dopant diffusion process in which the dopant diffusion process in which the dopant source is removed before completion in order that the peak of concentration is diffused-in below the surface so as to produce a graduated resistivity profile which increases nearer the surface. In shorted-emitter thyristors the surface region is masked during subsequent emitter diffusion so that the remaining short columns contain higher resistivity material.

Abstract: A control valve arrangement adapted to produce and maintain a pilot signal comprises a number of standard modules. The basic element has two standard modules, each of which includes a diaphragm-controlled on-off valve. An input signal is applied to a first valve against a reference pressure such that when the valve is on, a signal is generated and held as a pilot pressure. A second valve responds to a fall in input signal pressure to cancel out pilot pressure. The two valves together constitute a bistable operator. A particular use of this operator is in a railway braking system in which the first valve is used as an application valve and the second valve is used as a release valve. A third module may be used as a pilot pressure-maintaining valve. The pneumatically-operated diaphragm assembly shown in FIG. 1, comprises three modules, 1, 2 and 3. Module 1 is the brake application module, module 2 is the release module and module 3 is an optional pilot pressure-maintaining module.

Abstract: This invention relates to braking systems for railway vehicles in which a fall in brake pipe pressure is employed to initiate braking via a brake cylinder inlet valve.In accordance with the present invention, the brake cylinder inlet valve is rendered in-operative by the absence of auxiliary reservoir pressure, thus dispensing with the need for a complicated mechanical sequence requiring fine machining tolerances etc. and avoiding the necessity of employing an additional valve.The brake cylinder (BC) inlet valve 60 is operable by a diaphragm 54. When the system is fully charged, the brake cylinder inlet valve 60 is closed as shown in the accompanying drawing. The diaphragm 54 is subject to brake pipe pressure in chamber C and to auxiliary reservoir pressure in chamber D. In the absence of auxiliary reservoir pressure in chamber D, the pressure in chamber C holds the diaphragm in the position shown and prevents the ball valve 60 from being opened, thus preventing brake application until braking is demanded.

Abstract: A road brake automatic slack adjuster mechanism having input and output members each pivotable about a common axis to apply and release a brake-applying force. These two members are interconnected by a force-transmitting member which, on the one hand, is threadedly engaged with the output member and, on the other hand, is releasably clutched to the input member. To effect slack adjustment, the mechanism includes brake-clearance determining device settable to predetermine the required brake clearance. This brake-clearance determining device includes a stepless clutch which interconnects the brake-clearance determining device and the output member. The clutch is released upon pivotal movement of the output member in a brake-force applying direction, equating with the required brake-clearance to allow the clutch to slip during movement of the output member corresponding to excessive clearance.

Abstract: A plug-in "universal" information display module for use in an information display system, e.g. a train describer system, of the kind in which all information to be displayed is multiplexed onto a data highway routed to all display locations. The heart of the module is a microprocessor which "listens" to the multiplexed messages on the data highway, selects for decoding only those containing the address of its location and produces a decoded message in the form of a two-dimensional matrix display format suitable for scanning to drive an L.E.D. matrix display panel. An address programming means is connected to an address input to the microprocessor so that a module is normally programmed with a location address at the time of connection to the data highway either by a manual operation or automatically upon mating of the plug connector.

Abstract: A railway vehicle braking system is provided with snow-brake control means operable in freezing temperatures for overriding the normal full brake release condition in a vehicle coasting or traction situation to apply a small brake force for prolonged periods to engage blocks or shoes on the vehicle wheels to reduce icing. The snow brake control means itself includes an override arrangement for, from time-to-time, effecting complete but temporary release of such a snow brake application so as to enable whatever slack adjustment is necessary to thereby insure continued validity of the brakes for a service application despite brake wear resulting from prolonged snow brake application.

Abstract: An electronic or computer-based railway control system including further safety checks in addition to normal safety interlocking. The present system carries out checks to see that operations, such as print switching and signal setting, are carried out in the correct sequence for a given route having regard to the position and movement of a train as indicated by track circuits. In a computer-based system appropriate checking routines may be written into the computer soft-ware.