Patent GB-635128-A (GB)
Title: Improvements in or relating to route finding devices
IPC: G06G7/122
Filed: 1946-11-29
Abstract: 635,128. Monogrammic signs. HANSFORD, R. F., and SPERRY GYROSCOPE CO., Ltd. Nov. 29, 1946, Nos. 35467/46 and 7737/47. [Class 118 (ii)] A route finding and indicating device comprises a plurality of points interconnected by a maze of channels in each of which one, or more, threshold operated indicating devices are incorporated or coupled by means of impedance transforming devices, means for connecting to one of the points and to any selected other of the points input and output channels for a. working agent and impedance means for dissipating or absorbing some of the pressure or force of the working agent connected in the input or output channel or in both. In a preferred manner of carrying out the invention the device comprises a base member 10, Fig. 1, carrying an electrical network including a plurality of neon glow lamps 15 suitably disposed in relation to openings 13 in an opaque sheet 12 on which is presented a map display representing a railway network system. The number of lamps 15 included in each route (i.e. each channel of the network) between a station such as Z, Fig. 2, at which the indicator is located and the other stations a to o on the system is made proportional to the average time of travel over each route additional lamps 15<SP>1</SP> being included at points representing stations of interchange. In the operation of the indicator, which is arranged to indicate the shortest route between station Z and any of the stations a to o, a source of A.C. voltage is applied between Z and a selected station by means of pressel switches A, O and, as this voltage rises from zero in any half cycle it reaches a value equal to the sum of the ignition voltages of the lamps 15 which are included in the shortest route, any further increase in voltage tending only to increase the current flow through the lamps already ignited so that, by virtue of resistor 19, the voltage across the network is maintained constant at a value which is less than the ignition voltages of the lamps in paths other than the shortest. The latter path (route) is therefore indicated visibly and the reading of the voltmeter 20, which depends on the number of lamps ignited, gives a measure of the distance or transit time between the station Z and the selected station. Should there be two or more routes between the latter stations comprising an equal number of lamps a permanent bias voltage in favour of, or against, a particular route or routes is introduced so that only a single, preferred, route is indicated. To reduce the high transformer secondary voltage, which must be equal to the sum of the ignition voltages of the lamps included in the shortest route between the two most distant stations, the lamps may be coupled to the network by means of step-up transformers (Fig. 3, not shown). By employing a D.C, supply the transient effects resulting in partial illumination or flickering of lamps associated with routes not included in the desired route may be avoided. Instead of carrying out the invention electrically the energy source may comprise a fluid under pressure, in which case the electrical network is replaced by a system of conduits or pipes, the neon lamps by spring-loaded valves and the resistor 19 by a constricted nozzle or any device which causes a pressure drop when the fluid flows through it. The indication in this case may be afforded by displacement of the valves included in the route or by any form of flow meter.