Patent GB-881721-A (GB)
Title: Improvements in or relating to systems for detecting and recording vehicle movements
IPC: G08G1/127
Filed: 1957-10-29
Abstract: 881,721. Electric selective signalling systems. BRITISH TRANSPORT COMMISSION, and READMAN, A. Oct. 27, 1958 [Oct. 29, 1957], No. 33758/57. Class 40 (1). In a system for identifying particular objects during movement e.g. omnibuses, and recording their movements, each object is provided with a plurality of spaced markings which when traversed through a light beam emanating from a check point reflect the light in accordance with the passing objects' identifying number in binary form. The system, Fig. 1, applied to a bus service, comprises a series of check points 12, 13 placed alongside a bus route and each bus of the service carries a plate 10 with reflectors 11 which in passing through the light beam at a check point reflects the light in accordance with its binary number. The reflected information is read into unit 13 and stored until the reception of the final reflected pulse triggers a read-out arrangement which passes the information via line A, B to a control centre 14 where the bus position is displayed. Scanning unit (Fig. 2, not shown).-The light projected by scanning unit 12 of the check point equipment is chopped at a frequency of 5000 c/s. and forms a beam which is narrow in the horizontal plane and somewhat wider vertically, to ensure its impingement on the reflector plate of a bus. The bus reflectors are of a type which reflect light back along the incident beam; each of the five leading vertical pairs of reflectors is coloured either white or red, one colour corresponding to one digit of the binary code, and the sixth pair of reflectors is of a colour complementary to red. On reflection the light beam is split and passed to two photo-electric cells 28, 29, one of which responds to white light signals and signals of the colour complementary to red and the other responds to white and red signals. The output of the latter circuit consists of timing pulses and the output of the former produces the code pulses and a final read-out pulse. The separate trains of pulses are demodulated 12a, 12b and the pulses are reformed in a shaper 13a, 13b. Read in and storage circuit.-The timing pulses are applied at point PB7, Fig. 5, to an upper row of gas triodes V12-V17 and the code pulses at point PB3 to a lower row of triodes V19-V23. In operation V12 is normally conducting and its cathode circuit provides a positive bias for the trigger grids of V13 and V19, on arrival of a timing pulse V13 fires and by feeding back its anode pulse via C19 extinguishes V12. If a code pulse is received V19 fires and remains in this condition until the complete code train is accepted and signalled to the control centre. The cathode circuit of V13 now provides bias to the next pair of valves V14 and V20. In this way the upper valves condition the lower valves in turn for the acceptance of a code pulse and the code number is represented by the conducting or non-conducting condition of valves V19- V23. The number is also stored in the energized or de-energized condition of a series of fine relays connected in the anode circuits of the valves. Read out circuit (Fig. 6, not shown). The information is read out to the control centre via line A,B when the reception of the code signal is completed. The final timing valve V17 and valve V23(a) together operate a relay which commences the operation. The arrangement comprises an oscillating relay circuit which connects a D.C. source to the line A,B via contacts of the five relays in turn and the polarity of the connection is determined by the energized or de-energized state of the relays. After the transmission of the five positive or negative pulses a sixth negative pulse is transmitted to signal the completion of the code signal. Control office equipment (Figs. 7 and 8, not shown) -Five translator relays reproduce the binary signal at the control centre and contacts of these relays and those of three auxiliary relays are connected in a contact " time " which is arranged to convert the binary code number to the omnibus number in decimal form. On receipt of the final negative pulse from the control point a condenser is discharged through the contact " time " and strikes a lamp allocated to the check point in the group of lamps allocated to the particular omnibus.