US3278933A - Identification system - Google Patents

Description

0st. 11, 1966 P. HOMAN ETAL 3,278,933

IDENTIFICATION SYSTEM Filed April 30, 1964 2 Sheets-Sheet l CARRIER WAVE oscILLATOR C5, 5 MODULATOR M1 3 2 3 3 E M SUPPLY V V 51 ,1 Tic-F S2 1 B2 5 *fi cs 53 CHILI 3 L I.

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'TON B GENERATOR DETECTOR ODER sEPERATIoN 5 FILTERS P E:}I I 3 AMPLIFIER AMPLIFIER I NVEN TORS PIETER HOMAN JOHANNES M/K AGENT Oct. 11, 1966 P. HOMAN ETAL 3,278,933

IDENTIFICATION SYSTEM Filed April 50, 1964 2 Sheets-Sheet 2 GENERATOR H E E ZE/ Fl TONE GENERATOR I 12 13 Fzl s 15 11 4 f DETECTOR DECODER KI AMPLIFIER GATE COUNTER INVENTORS P/ETER HOMA N J 0 HA NES Mllf AGENT 3,278,933 IDENTKFECATEGN SYSTEM Pieter Homan, Utrecht, and .iohannes Mik, Nienw-Loosdreclit, Netheriands, assignors to North American Philips Qompany, inc New York, N.Y., a corporation of Delaware Filed Apr. 30, 1964, Ser. No. 363,847

Claims priority, application Netheriandls May 8, 1963,

12 Ciaims. (Cl. 343-6.5)

The invention relates to an identification system for moving objects and more particularly to an identification system employing a sending unit fastened to a relatively moving object which travels along the receiving station and causing an identification code, fixed in the identification unit and consisting of a plurality of signs, to be transmitted to the reading station by means of electromagnetic signals.

For use on railway carriages, particularly railway vans efforts must be made to obtain durability, simplicity and economy for the identification units to be fastened to the vans, so that the units can be readily mounted on vans of highly different construction, without the need for delicate or sensitive component parts. Such identification systems are known from German Patent Application No. 1,140,245 laid out for public inspection, and from an article Die Technik der Giiterwagenidentifizierung by Dr. Ir. Hans Ulrich Meyer in Signal und Draht 54 (1962) 1.

When using known identification systems, difficulties arise with a code consisting of 7 or more decimal signs, particularly, with a 3 meter antenna and a train speed of 160 kms/ hour or more.

In the European railway system identification codes of 12 to 14 digits are universal and reliable reading at a train speed of 160 kms./hr. and an antenna length of about 3 m. must be provided.

The identification system according to the invention is capable of satisfying the said requirements. In achieving the requirements, each of the signs of the identification code are characterized by one or more audio-frequency signals which are transmitted simultaneously for a plurality of identfying signs.

With the known systems the signs of the identification code are transmitted in order of succession. In connection with building-up times a certain period of time is required for the reliable recognition and transmission of one sign, while after the reception and recording of a sign at the reading station time is required for changing over the apparatus to the transmission of the next-follow ing sign. In the case of railway vans the length of the receiving aerial at the reading station is restricted in order to avoid simultaneous coupling with the identification units of two vans of one train. The time required for the transmission of all signs of the identification code and the chosen length of the receiving antenna are determinative of the maximum speed of the train at which a reliable identification of a van is still possible.

When applying the invention, the above drawbacks are obviated by simultaneous transmission of all signs or of at least a plurality of signs of the identification code, so that the time of recognition per sign corresponds with the maximum time of observation or with a considerable part of said time, for example half of it.

The desired simultaneous transmisison may be carried out by using a frequency-multiplex transmission system, a timemultiplex transmission system, or a suitable combination of these two systems.

The term time-multiplex transmission is used to denote herein a transmission system in which successive signs are scanned with a frequency which is materially higher than the maximum sign frequency to be transmitted, for example at least two-and-a-half times higher.

Patented Oct. I1, 1966 When a frequencymultiplex system is employed it is desirable for practical reasons to choose the carrier frequencies used for the transmission to be lower than about 150 kc./sec., owing to disturbances which may be produced by the system in radio communications and to the intereferences to be expected in the identification system, as, for example, when a reading station is established in the vicinity of a long-wave or medium-wave transmitter.

In order to transmit the comparatively broad frequency bands used in a time multiplex transmission system, for example of 40 to kc./sec. in the case of 7 to 13 signs, it is desirable to transmit these broad frequency bands on carrier frequencies which are very high for practical reasons, for example 20 to 30 mc./sec. These comparatively high carrier frequencies require low carrierwave powers for transmission of the signal from the moving object to the reading station, since interferences from neighboring radio transmitters have a comparatively low level and the disturbances due to traction currents in this frequency range are also slight.

In order to ensure a reasonable transmission the modulation frequency should preferably not exceed about 1 to 2% of the carrier frequency, so that in connection with the foregoing the modulation frequencies are limited to about 1500 c./sec. at the most. When a plurality of carrier waves are employed, the maximum modulation frequency is determined by the lowest carrier freqency and this involves the choice of audio-frequency signals within the speech range from 300 to 3400 c./sec., preferably standard telegraph frequencies with intervals of c./sec. for characterizing the signs of the identification code.

The invention will now be described more fully hereinafter with reference to a few examples shown in the diagrammatic drawing.

FIG. 1 shows a simplified circuit diagram of an identification unit according to the invention.

FIG. 1a shows a variant of the current supply unit for the device shown in FIG. 1.

FIG. 2 shows the principle of the receiving device in a reading station co-operating with identification units as shown in FIG. 1.

FIG. 3 shows a further embodiment of an identification unit.

FIG. 4 shows the receiving device co-operating with the identification unit of FIG. 3.

The identification unit shown in FIG. 1 is intended for an identification code of a plurality or group of 7 indicia representing 7 decimal digits, simultaneously transmitted by means of 7 carrier waves each having an electrical characteristic indicative of the position of each indicia in the group. Each of these carriers are amplitude modulated by 2-out-of-5 characteristic tone frequencies. The supply unit 1 provides two different direct voltages to the power lines 2, to which are connected seven carrier wave oscillators CG CG and five tone generators AG AG The supply unit 1 may be any direct current source, but for railway vans a battery or another carried current source is not practical for the reasons mentioned above. In the above embodiment, the supply energy is obtained by electromagnetic energy emanating from the reading station and transferred to the receiver by means of the receiving coil L Coil L together with the capacitor C constitute a circuit tuned to the supply frequency which circuit is connected to the power lines 2 through the rectifiers B and E the direct voltages being smoothed therein by the capacitors C and C As soon as the receiving coil L arrives within the range of the transmitter loop, it is energized by the supply frequency of the reading station, the direct voltages generated are supplied to the power lines 3 2, and the said seven carrier wave oscillators and the five tone generators become simultaneously operative.

The reading station arranged alongside the track can be rendered automatically operative by an approaching train by means of a suitable signal, derived for example from a current circuit of the track, so that the transmitting loop of the reading station is already energized by the supply energy of the chosen supply frequency and the receiving members of the reading station are ready for reading the identification codes, when the first identification unit of the train, fastened to the first carriage thereof, reaches the reading station.

In the coding matrix M of each identification unit the tone frequencies are transmitted in accordance with the identity of the van concerned from the primary line P I P to the secondary lines S S In the given example it is assumed that the 2-out-of-5 code is composed as follows:

Digit P1 P2 P3 P4 P5 1 X X 2 X X 3 X X 4 X X 5 X X 6 X X 7 X X 8 X X 9 X X X X The coding matrix M in the example shown in FIG. 1 is adjusted to the code 4071678.

In this way the first carrier wave oscillator CG receives the two-tone frequencies supplied through the first secondary line S simultaneously by the first tone generator AG along the primary matrix line P and the fifth tone generator AG along the primary matrix line P The coupling in the matrix indicated by dots at the crossings must be kept comparatively weak, for example by inhibiting impedances, since each tone frequency must be simultaneously int-roduceable in a plurality of secondary lines. In the embodiment shown the second tone frequency across the second primary line P is applied simultaneously to the four secondary lines S S S and S A further reason why the matrix couplings must be weak consists in that for example (FIG. 1) the second tone frequency must not reach through the three couplings P 8 S P and P 8 the line S on a disturbing level. It is furthermore desirable for the coding matrix to be readily variable.

The audio-frequencies af and af transmitted by the primary lines P and P to the secondary line S are modulated by the modulator CM on the first carrier frequency cf which is transmitted with this modulation. This may be carried out by means of a ferrite rod F which constitutes a common core for the inductors and coupling coils of the carrier wave generator CG and the modulator CM In an analogous manner the other carrier waves cf Cfq are each modulated by two of the five audiofrequencies af 117%.

The characteristic audio-frequencies may as an alternative be produced in the reading station and be modulated on the supply frequency. The supply unit of each identification unit shown in FIG. 1a then furnishes, subsequent to rectification (B B of the incoming energy, a direct voltage with the superimposition of the five tone frequencies. The direct-current energy is applied through the low band-pass filters LF and LF to the carrier wave generators CG CG- whereas the five audio-frequencies are applied to five tone filters taking the place of the tone generators AG .AG of FIG. 1 and applying the same tone frequencies af af to the primary matrix lines P .P respectively.

The receiving member in the reading station for the signals emanating from the identification unit of FIG. 1 is shown diagrammatic-ally in FIG. 2.

The antenna loop 3 receives seven carrier frequencies simultaneously, each modulated by two out of five available tone frequencies for the whole duration of the available reading time. After amplification in the antenna amplifier 4, the seven carrier frequencies are separated from each other by the filters CF .CFq. The output of each of these filters has connected to it an ampli tude detector D D of which only the first (D is shown in FIG. 2. The detector D supplies the two audiofrequencies by which the first carrier frequency cf is modulated: in the embodiment shown in FIG. 1 the two audiofrequencies af and 113. Subsequent to amplification in the low frequency amplifier 5, these frequencies are applied to a common input of a group of five tone filters AF .AF of which in the embodiment shown only the filters AF; and AF will each supply an output signal, whereas the further three filters AF A1 and A1 do not produce an output signal, since the relevant tone frequencies are lacking.

The outputs of the five tone filters are connected to a 2/5 decoding circuit 6, which produces the first sign 4 in the embodiment shown) of the identification code in a form suitable for further processing, for example for perforation of a tape or for telex transmission to a central control-station.

Each of the seven carrier wave filters 0P CF has connected to it an identical group consisting of a detector D, a low-frequency amplifier 5, a group of five tone filters A F AF and a 2/5-decoding circuit 6.

The number of carrier waves, which is only seven in the embodiment shown, may be extended without any objection. In the range from 45 to 146 kc./sec. thirteen carrier frequencies can be arranged with an interval of 10% between adjacent carrier frequencies, each of said frequencies of 420, 540, 660, 780, and 900 c./s. tone frequencies, which may be the standard telegraph frequencies of 420, 540, 660, 780, and 900 c./ sec.

FIG. 3 shows diagrammatically the identication unit of an embodiment in which the characteristic tone frequencies associated with the 13 digits of a decimal identification code are simultaneously transmitted in time multiplex by means of a single carrier frequency. The supply unit is not shown in FIG. 3; it may be similar to that of FIGS. 1 or 1a. The five tone generators or tone filters AG AG feed the primary line P P of the coding matrix M by five tone frequencies, which are transmitted, in accordance with the identification code, in the same manner as in the preceding example, to the 13 secondary lines S S which are each in turn connected to a normally cut-off gate circuit G G Consequently each input of the gates receives a mixture of 2 out of 5 tone frequencies. The controlelectrodes of the gate circuits are connected to the thirteen outputs of an electronic ring counter, where pulses of short duration are cyclically passed. When the ring counter 7 is driven in a rhythm of 3000 c./sec., the gates will be opened each 3000 times per second for a short time, for example about 10 1.860. and will then pass the instantaneous value of the input voltage consisting of two tone frequencies. The short pulses passed are, however, sufficient for the two input tone frequencies to be completely determined. Since the opening of the gates is controlled in a cyclic order of succession by the ring counter, a continuous series of pulses of varying magnitude with constant intervals appears at the common output in a frequency of 3000 13=39000 c./sec. This signal is modulated by the modulator 9 on the carrier frequency of for example 27 mc./sec. supplied by the carrier generator 8, which is transmitted with this modulation by the antenna 10.

In the reading station the receiver shown in FIG. 4 receives the signal via the antenna 11 and subsequent to amplification in an amplifier 12 the pulses obtained by detection in a detector 13, are applied to the common input of a group of 13 gate circuits G G controlled by a ring counter 14 in synchronism with the control of the gate circuits G G of FIG. 3. The gates G G then pass the pulses emanating from the common detector 13 at such instants that at the output of a given gate G only those pulses appear which represent the mixture of the two characteristic tone frequencies of the relevant digit of the identification code. The transmitted digit can be restored therefrom by means of five tone filters AF AF and a 2/ S-decoding circuit 15.

The synchronization of the ring counters 7 and 14 may be obtained in various known ways, for example a fourteenth sign may be added to the thirteen desired digits for marking a given place in the scanning cycle.

The identification system according to the invention permits of reading in a reliable manner twelve or more signs of an identification code with a speed of a train of 160 kms./hr. or more and with a length of the antenna loop of not more than 3 meters, while various further advantages are obtained by the system according to the invention. In the presence of a carrier wave and in the absence of the audio-frequency code it permits of signalizing positively the lacking of the latter. The tone filters at the receiver end, having a restricted bandwidth, provide automatically a recognition period of m. sec. or more for each of the tones, so that only tone frequencies received during at least said period of time will be recorded or transmitted. This means a great insensitivity to disturbances such as due to sparks between the aerial contact line and the current pick-ups or somewhere else in the heavy-current system of a train. Owing to the simultaneous reading as in the embodiments shown the said long period of recognition is amply available for each sign, since all signs of the identification code can utilize the whole period of reading.

It should be noted that the identification system described above operates independently of the direction of travel, so that the reading of the identification code is not disturbed for example by oscillatory motions of the identification unit due to buffer phenomena at the place of the reading station.

What is claimed is:

1. Apparatus for transmitting from a moving object to a spaced receiving location information identifying the said moving object and constituted by a plurality of indicia arranged in consecutive order, said apparatus comprising at said movable object a first voltage source supplying a plurality of indicia position voltages, each of said voltages having an electrical characteristic indicative of the position of a different one of said plurality of indicia in said consecutive order arrangement, a second voltage source supplying a plurality of indicia characteristic signal voltages for indicating the numerical value of a respective one of said indicia, means for modifying the amplitude of each voltage of said first source in accordance with respective ones of said indicia, and means for simultaneously transmitting all of said modified first source voltages from said moving object to said receiving location.

2. The combination of claim 1 wherein said first source of voltages are generated by a plurality of oscillators, each generating a different frequency respectively indicative of the position of one of said indicia in the said consecutive order.

3. The combination of claim 1 wherein said first source of voltages are generated by an arrangement including an oscillator, and switching means connected to said oscillator, said switching means providing a plurality of output voltages from said oscillator, each of said output voltages having the same frequency but time displaced relative to one another in the said consecutive order.

4. The combination of claim 1 wherein said means for modifying comprises modulation means, a coding matrix, said matrix having a plurality of conductors arranged in overlapping rows, and columns, said modulating means connecting each of said first source voltages to a respective one of said rows, each of said second source voltages being connected to a respective one of said columns, said matrix arranged so that selected ones of said row conductors contact selected ones of said column conductors at selected points of overlap, the signals from certain ones of said second source voltages modulating respective voltages of said first source voltages through each of the said selected points.

5. The combination of claim 4 wherein each of said first source voltages is modulated by selected combinations of two of said second source voltages.

6. A signal identification system including a transmitter and receiver, said transmitter generating a uniquely coded signal constituted by a plurality of indicia arranged in consecutive order and comprising a plurality of carrier wave oscillators, each having a unique relatively high frequency carrier output indicative of the position of said indicia arranged in consecutive order grouping, a plurality of tone generators, each generating a unique relatively low frequency signal indicative of the numerical value of a respective one of said indicia, means for applying energy to said oscillators and generators, a plurality of multi-input modulators, means connecting the output of each of said carrier oscillators to an input of a respective one of said modulators, means connecting selected ones of said tone generators to the inputs of selected ones of said modulators, the signals from said generators modulating the signals from said oscillators through said means connecting so as to form a predetermined code uniquely representative of said transmitter, and means for simultaneously transmitting all of said modulated oscillator signals from said transmitter to said receiver.

7. The combination of claim 6 wherein said means connecting comprises a coding matrix, said matrix having a plurality of conductors arranged in overlapping rows and columns, means connecting each of said oscillators to a respective one of said rows, each of said generators being connected to a respective one of said columns, said matrix arranged so that selected ones of said row conductors couple selected ones of said column conductors at selected points of overlap, the signals from certain ones of said generators modulating the signals from each of said oscillators through each of the said selected points.

8. The combination of claim 6 wherein said means for applying energy to said oscillators and generators includes a tuned circuit responsive to a single frequency and a rectifier coupling said circuit to said oscillators and generators whereby said oscillators and generators are simultaneously energized upon application of said single frequency signal to said tuned circuit.

9. The combination of claim 6 wherein said receiver comprising a plurality of carrier separation filters responsive to the transmitted signal, the number of said carrier separation filters equalling the number of carrier wave oscillators present in said transmitter, the output of each of said carrier separation filters being coupled to a plurality of tone filters, the number of tone filters equalling the number of tone generators present in said transmitter, and a plurality of decoders, each of said decoders being connected to the combined output of each said plurality of tone filters, all of said decoders having a combined output indicative of the predetermined unique code set in the associated transmitter.

10. The combination of claim 6 wherein said matrix arrangement is such that each of said carrier wave oscillators is modulated by two of said tone generators.

11. A signal identification system including a transmitter and receiver, said transmitter generating a uniquely coded signal and comprising, a carrier wave oscillator,

modulating means connected to said oscillator, a plurality of tone generators, a coding matrix, said matrix having a plurality of conductors arranged in overlapping rows and columns, means connecting each of said generators to a respective one of said columns, a cyclically operable multi-stage transmitter switching unit, said unit having as many stages as there are rows in said matrix, a plurality of transmitter gating devices each having provision for a gating input and a signal input, the signal input of each transmitter gate being connected to a respective row conductor, and the gating input of each of said transmitter gate being connected to a respective stage of said switching unit, means commonly connecting the output of each transmitter gate to said modulating means, said matrix being arranged so that selected ones of said row conductors are coupled to selected ones of said column conductors at selected points of overlap, the signals from certain ones of said generators modulating the signal from said oscillator in said modulating means through each of the said selected points when the respective gating device is energized, whereby an electrical manifestation of a predetermined code is formed at the output of said modulating means, said transmitter transmitting said electrical manifestation to said receiver, said receiver comprising, a detector responsive to the said electrical manifestation, a cyclically operable multistage receiver switching unit having as many stages as there are rows in said matrix, a plurality of receiver gating devices each having provision for a gating input and a signal input, the signal input of each receiver gate being commonly connected to said detector, the gating input of each transmitter gate being connected to a respective stage of said receiver switching unit, the output of each of said transmitter gate being connected to a plurality of tone filters, the number of tone filters equalling the number of tone generators present in said transmitter, and a plurality of decoders, each of said decoders connected to the combined output of each of said plurality of tone filters, all of said decoders having a combined output indicative of the predetermined unique code set in the associated transmitter.

12. The combination of claim 11 wherein said cyclically operable multistage transmitter switching unit and said cyclically operable multistage receiver switching unit are synchronized one to the other with reference to a common time base.

References Cited by the Examiner UNITED STATES PATENTS 2,470,145 5/1949 Clos 340-171 2,658,189 11/1953 Lovell 34017l 2,910,579 10/ 1959 Jones et al. 343- 3,054,100 9/1962 Jones 3436.5 3,145,380 8/1964 Currie 3436.5'

CHESTER L. J USTUS, Primary Examiner.

P. M. HINDERSTEIN, Assistant Examiner.

Claims (1)

1. APPARATUS FOR TRANSMITTING FROM A MOVING OBJECT TO A SPACED RECEIVING LOCATION INFORMATION IDENTIFYING THE SAID MOVING OBJECT AND CONSTITUTED BY A PLURALITY OF INDICIA ARRANGED IN CONSECUTIVE ORDER, SAID APPARATUS COMPRISING AT SAID MOVABLE OBJECT A FIRST VOLTAGE SOURCE SUPPLYING A PLURALITY OF INDICIA POSITION VOLTAGES, EACH OF SAID VOLTAGES HAVING AN ELECTRICAL CHARACTERISTIC INDICATIVE OF THE POSITION OF A DIFFERENT ONE OF SAID PLURALITY OF INDICIA IN SAID CONSECUTIVE ORDER ARRANGEMENT, A SECOND VOLTAGE SOURCE SUPPLYING A PLURALITY OF INDICIA CHARACTERISTIC SIGNAL VOLTAGES FOR INDICATING THE NUMERICAL VALUE OF A RESPECTIVE ONE OF SAID INDICIA, MEANS FOR MODIFYING THE AMPLITUDE OF EACH VOLTAGE OF SAID FIRST SOURCE IN ACCORDANCE WITH RESPECTIVE ONES OF SAID INDICIA, AND MEANS FOR SIMULTANEOUSLY TRANSMITTING ALL OF SIAD MODIFIED FIRST SOURCE VOLTAGES FROM SAID MOVING OBJECT TO SAID RECEIVING LOCATION.

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