Abstract: A joint for joining a silicon disc (21) to a molybdenum disc (22) comprises a layer of titanium silicide (20) and a layer of aluminium-silicon solder (23). The titanium silicide is formed by depositing a layer of titanium on the silicon disc and heating the silicon disc and the titanium to around 550.degree. C. to encourage the formation of titanium silicide. A solder disc is then compressed between the silicon and molybdenum discs at about 690.degree. C. to fuse the solder to the titanium silicide layer and the molybdenum disc. The layer of titanium silicide protects the silicon disc from dissolution during soldering, so that diffused-in features in the silicon are not damaged.

Abstract: In a railway signalling system, to achieve inter-vehicle headway spacing for railway vehicles (1) travelling on a track (T), there are a) control of vehicles by fixed block signalling and b) control of vehicles by moving block signalling via communication between vehicles. The moving block signalling occurs within a moving block control zone of the track and the fixed block signalling occurs outside that zone, there being the facility of two-way data transmission between vehicles throughout the moving block control zone and the fixed block signalling system not preventing a further vehicle from entering the mowing block control zone when another vehicle is already in that zone and receiving a transmission via the moving block signalling system.

Abstract: A railway track circuit system is described, in which there is a transmitter 15,16 and receiver 19,20 at each end of a track circuit section 4. Each receiver receives signals from the transmitter at the opposite end of the section and the received signals are analyzed to determine whether a vehicle is present in the track circuit section. Where adjacent track circuit sections are also provided with a transmitter and a receiver at each of their ends, the transmitters 14,17 and receivers 18,21 at adjacent ends of adjacent track sections 3,5 can be connected to a track circuit unit 8,9 to allow that unit to check, when a vehicle appears to have left one track circuit section, that it has entered an adjacent section.

Abstract: In a railway signalling system, the length of a vehicle or train is computed by on board measurement of the distance travelled between detecting the passage of the front of the vehicle or train past a fixed point and detecting the passage of the rear of the vehicle or train past the same fixed point or a fixed point a known distance from the first.

Abstract: A circuit arrangement for detecting an input voltage comprises an oscillator responsive to the voltage, the oscillator including a pair of transistors (8, 9) connected as an astable multivibrator, each of the transistors having a load which comprises a primary winding (16 or 17) of a current transformer (T) and a low resistance proof resistor (12 or 13). A current flows through a secondary winding (18) of the transformer the amplitude of which current is proportional to the input voltage.

Abstract: A circuit arrangement includes a lamp filament (1) as a load and a resistor (2) in series with the filament. For detecting the current through the load, the source of a MOSFET (6) is connected with the end of the resistor remote from the filament, the drain of the MOSFET being connected with the other end of the resistor via the primary winding of a step-up transformer (7) and a further resistor (8), a diode (9) being connected between the source and the drain of the MOSFET. If the MOSFET is turned on by an appropriate voltage at an input (11) connected to its gate, the voltage across the secondary winding of the transformer is substantially proportional to the value of the current through the filament.

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: A tread-brake unit comprises a brake piston and arrangement (101/100), a slack adjuster (200) and a brake shoe (300). The piston (101) is mounted in the cylinder (100) such that in operation of the brake piston and cylinder arrangement the axis (103) of the piston (101) oscillates about the axis (104) of the cylinder (100). The axis (104) of the cylinder (100) is inclined with respect to the axis (201) of the slack adjuster (200) in the plane in which the axis (103) of the piston (100) is oscillatable about the axis (104) of the cylinder (100). The piston rod (105) of the piston (101)is pivotally engaged with one end of a first lever (401) pivotally mounted in the unit and engageable with one end of a second, bell-crank, lever (410) which is pivotally mounted at its elbow in the unit and is pivotally engaged at its other end to a part (280) of the slack adjuster (200) movement of which within the unit effects, through the slack adjuster (200), operation of the brake shoe (300).

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: A slack adjuster has a non-rotatable fast-threaded output member (19) threadedly engaged by a pair of nuts (20, 21), one of the nuts being a first brake-force-transmitting nut (20) clutchable to prevent rotation thereof and the other being a second adjustment nut (21) clutchable to land. Relative axial movement of these nuts relative to the output member (19) is a measure of "excessive" brake clearance and restoration of the normal spacing between these nuts serves to restore brake clearance to "normal". The nuts (20, 21) are housed in a housing (8) which is non-rotatable but axially movable with respect to the output member (19). The first nut (20) is clutchable to a thrust member (26) resiliently loaded with a force which is overcome only by forces of the magnitude of braking forces transmitted through the slack adjuster.

Abstract: A tread-brake unit copmrises, as a unitary structure, a brake shoe (300) for engaging a vehicle wheel tread, a brake actuator (100) having an output member (19) via which the brake shoe (300) can, firstly, be moved into engagement with the wheel tread and, thereafter, a braking force generated by the actuator (100) can be transmitted to the brake shoe (300), and a slack adjuster (200) by which clearance between the brake shoe (300) and the wheel tread, in the "released" condition of the unit, can be maintained substantially constant. The slack adjuster (200) has a pair of fast-threaded units (20,21), each nut being threadedly engaged with and rotatable on the output member (19) of the actuator (100).

Abstract: A railway signalling system includes a plurality of trackside equipments (11,12) and means (1,2,3,4,6, 15,16) for transmitting control information to the equipments and receiving status information therefrom, each of the trackside equipments being provided with a respective microprocessor (13 or 14) via which such control information is transmitted from the said means to the equipment and via which such status information is received by said means from the equipment.

Abstract: A circuit arrangement for providing in a fail-safe manner an alternating output signal to a load, e.g. in a railway signalling system. The load is connected across a first winding of a transformer, to opposite ends of a second winding of which transformer is connected a bi-directional current switching circuit. First and second modulated signal sources are connected to the bi-directional switching circuit. Each of the signal sources modulates a carrier signal with a modulation signal, the outputs of the signal sources being out of phase with respect to each other. The bi-directional switching circuit is operative to switch current through the second winding alternately in opposite directions at the frequency of the modulation signal. The circuit arrangement is such that if any of its components fails to operate correctly, the output appearing across the first winding is no greater than a threshold level.

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: In a railway vehicle safety system, a frequency modulated signal is transmitted to a vehicle informing, inter alia, of a safe maximum speed, the said speed being represented by the carrier modulation frequency. In addition, the frequency of the carrier may possess one of a number of alternative frequencies. Apparatus for analysing received signals to identify the carrier frequency and the modulation frequency employs a fast Fourier transform processor. In order to save computation time by eliminating useless calculations, a received signal is heterodyned by a local signal selected according to the carrier frequency identified and the base-band components are analysed to identify the modulation frequency.

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: An electric actuator which comprises an electric motor operable to a varying degree correspondingly to cause a spring to generate on an output member an output force which varies in accordance with the varying degree of operation of the electric motor.