Patent GB-1043809-A (GB)
Title: Improvements in or relating to apparatus for identifying articles
IPC: B61L25/04
Filed: 1964-09-29
Abstract: 1,043,809. Track apparatus. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. Sept. 29, 1964 [Oct. 2, 1963], No. 39613/64. Heading B7N. [Also in Division H4] In an interrogator-responder system for identifying passing objects, e.g. railway carriages, each carriage is provided with a coding disc which provides a characteristic response signal and is driven by an electric motor supplied with energy transmitted from the interrogator station. At the interrogator station, Fig. 1, transmitter ZE transmits energy at, for example, 20 kc/s., which is coupled via a frame aerial AE to a smaller frame aerial RE, Fig. 2 (not shown), on the passing carriage. After rectification and smoothing at CA, KB, this energy drives the motor M operating the coding disc, and also supplies transmitters ZC, ZN. The coding disc consists of magnetic material carrying a number of teeth on its circumference arranged to co-operate with reading head KN to provide the appropriate coding and also carries a number of equidistant holes which co-operate with reading head KC to provide synchronizing pulses. The pulses obtained from heads KC, KN are transmitted by transmitters ZC, ZN on, for example, 55 kc/s. and 105 kc/s. respectively. At the receiving station, Fig. 1, the identification pulses are supplied via receiver SN to a shift register SR under the control of shift pulses on lead BB, the shift register being reset to zero with each synchronizing pulse supplied by the receiver SC via a delay VR. As described, a two-out-of-five code is used and the time between each pair of sync. pulses corresponds to the five time slots for the corresponding code character. Seven characters plus a characteristic start signal of five mark elements make up a complete identification signal. Since the coding disc motor does not reach a constant speed immediately, the time interval between sync. pulses will not be constant and a testing device is provided which controls the shift pulses in dependence upon the duration of the preceding period between two sync. pulses. The testing device includes a pulse generator GR providing pulses at a frequency f 0  which is high with respect to the pulse repetition frequency of the code signals. Generators GR supplies a counter TC and a frequency divider FD dividing by ten which supplies pulses to gates PA, PB controlled in opposite phases by a bi-stable trigger FA operated by the sync. pulses from receiver SC. The bi-stable device FA also resets counters TA, TB alternately. Thus the count is TA, TB count alternately between sync. pulses, their final position representing the duration of the preceding period. During the period in which the counter TA is not counting a coincidence circuit CA is made operative by the trigger FA and compares the final position of counter TA with the constantly varying position of counters TC, a coincidence circuit CB operating in a similar way when counter TB is not counting. The counter TC is reset by each sync. pulse via gate MP and will reach a position corresponding to the final position of say TA in a period of time equal to one-tenth of the duration of the preceding period between sync. pulses. When the counters TA, TC reach equal counts CA supplies a pulse to change-over bi-stable device FB and reset counter TC via gate MP and counter TC starts counting again until the final count of TA is reached, and so on. Thus, for each character period ten pulses are supplied by CA which correspond to the centre and end of each code element time slot, CB supplying the pulses during the following period. The bi-stable device FB ensures that only the pulses corresponding to the centre of each time slot operate the shift register SR. When a complete code character is recorded in the shift register SR the code elements are checked by a coincidence circuit CC and if it consists of the start signal of five marks a pulse is supplied to set bi-stable device FC so that gates PE and PD are enabled and a counter TD is reset to its rest position. The next sync. pulse resets shift register SR and TD counts a step and during the following period the first digit code group is recorded at SR, the counter TD takes a further step and a pulse is applied to a horizontal conductor of a matrix MG of bi-stable magnetic cores so that the first code group is recorded on a line M 1 , M 12  &c., the shift register SR being reset to zero. The remaining code digits are similarly stored in matrix MG and when the start signal appears again the circuit CC supplies a pulse which restores the trigger FC to the reset condition so that gates PE and. PD are blocked and a pulse is supplied over lead BX to indicate that the identification code has been received. By means not described, the information in matrix MG is read and it is returned to the rest state.