US1803454A - System for communicating with moving vehicles - Google Patents

Description

May 5, 1931. H. A. AFFEL 1,303,454

SYSTEIQFOR COMMUNICATING WITH MOVING VEHICLES Filed March 30, 1928 INVENTOR Eflflfie BY ATTORNEY Patented May 5, 1931 UNITED STATES,

PATENT OFFICE mm A. Arr-rm, or ntoenwoon, NEW JERSEY, ASSIGNOR 'ro AMERICAN TELE- moan AND TELEGRAPH com-rm, A conronerron or new YORK SYSTEM FOR COMMUNICATING WITH MOVING VEHICLES Application filed March 30, 1928. Serial No. 266,092.

The invention relates to improved arrangements for establishing communication between a fixed transmission system and a.

a moving. vehicle, such as arailroad train. In certain systems of the above type it has been proposedto transmit the signals along a line circuit paralleling the railroad trackand to transfer the signaling energy across the gap between the fixed portion 0 the sys- 1 tem, such as a transmission line, and the movable portion, such as the train, by induction. It has also been proposed to utilize relatively high frequency currents rather than ordinary voice currents, asithas been found that better coupling is obtained at the higher frequencies and hence there can be secured a greater transfer of ener across the, gap to and from the moving vehiclethanin the case of relatively low frequency signaling curgn rents.

' The use of high frequency currents in systems of this type'to overcome the induction attenuation across the gap between train and line presents certain problems in conzu -nection with the attenuation to be encountered on the line circuit, as in general high frequencies are subject to greater attenuation on the line than low frequencies. Also, the transmission in the direction from the movgo ing train to the fixed station presents a particularly serious problem because the transmitting level on the train must be sulficient to overcome the induction attenuation and provide on the wire circuit a level substans tially above the level of the line noise. Ac-

cordingly, it is the primary object of ar-' rangements of this invention to provideia fixed transmission system for min communicating with a moving vehicle, which will 40 permit high frequency currentstofbe \uti lized to reduce induction attenuation across the gap and in which the attenuation of such currents on the line will be materially reduced. Further objects and .features of the invention will a the detailed descriptmn thereof hereinafter The invention-inn be more fully understood from the 0 owing description 'to-.

gether with the accompanying ini is or pear more fully from.

the Figures 1, 2 .and 3 of which the invention is illustrated. 1 In Fig. 1 is a circuit diagram embodying a preferred form of the invention. Fig. 2 shows a modification of a por.

tion of the arrangements of Fig. 1. Fig. 3 shows'a modification of another portion of the arrangements of Fig. 1. Similar reference characters have been utilized to denote like parts in all of the figures.

In the arrangements of Fig. lis shown a track T onwhich would be a moving vehicle, such as the car 0. 'In the car .0 is shown a loop or antenna D to which would be connected high frequency carriertransmitting and receiving apparatus. In the vicinity of the track would be located a transmission line L. With one end of the line L would be associated high frequency carrier transmitting and receivin appai atus, such as 8'. Thelongitudinal circuit of the transmission line would be divided into certain sections, such as A and B, by means of inductance coils, such as 1 and 2. Connected to each of these line sections would be a translating device, such as 3.

Considering the transmission from the train to the fixed station, the high frequency carrier currents in the loop D on the train would be transmitted across the gap from the train to the transmission line L by induction and would traverse the conductors of the line in parallel with ground return due to the capacity between the conductors and earth, as indicated by the condensers 4,, shown in dotted lines. In other. words, under such conditions the line circuit L would operate as a longitudinal circuit with ground return. It is pointed out that the attenuation between a lon itudinal circuit of this type and earth dinarily high as compared. to the attenuation between a air of conductors form-e ing a metallic circuit and a greater amount of line noise is generally found on the Ion. gitudinal circuit. Furthermore, the longer the longitudinal line circuit the. greater wouldbe suchattenuation. According] the lon 'tudinal line circuit is, in accor anoe wit the arrangements of theinvention, brolren up into a number of sections by the 'inl .duction coils, such as 1 and 2. The windings 10.

ampli of these induction coils are arranged to be parallel aiding and hence produce a large flux in the core and a high impedance to the longitudinal currents. As the windin s are series opposed the flux is negligible, and ence the impedance in a metallic c1rcu1t would be neglig ble. Bridged across each longitudlnal section of the line would be a transformer winding, such as 5. The mid-point of this winding would be connected to ground through the filter 6 which is connected to the in ut of a translating device such as the er-demodulator 7. Connected to the output of the amplifier-demodulator 7 would be a filter 8'which might suppress undesired modulation products, and a winding .6 induc- V tively related to the winding 5. The longitudinal currents induced in the section A-of the line circuit by the currents in the loop D in-the car might take the path sho wn by the arrows (Z. 'These currents in passing through the winding 6 would induce currents in the winding 5, which currents would be applied to the sides of the line circuit L in series or as if the line were now a metallic circuit. These currents are indicated b the arrows cl; These currents would readi y be transmitted through the induction coils, such as 1 and 2, as the line would now be operating as a metallic circuit. Accordingly these 7 currents would be transmitted metallically to the apparatus8 at the end of the circuit. Ashas been previously pointed out, the attenuation of the signal currents when transmitted over a metallic circuit is smaller than when these currents are transmitted over a lon 'tudinal circuit and the si als are less :sub ect to line interference w en they are ously less subject to attenuation in transmission over the line circuit. Accordingly, the arrangements of the invention elfect a large reduction in the attenuation of the currents in transmission over the fixed portion of the system, both by reducing the frequency of such currents and transmitting such' currents metallically rather than longitudinally.

Transmission from the fixed station to the train might be accomplished without a change in the signal frequency, according to the general method described in my copending application, Serial No. 266,091, filed March 30, 1928,-or it might be carried out in a manner precisely the reverse of that described for transmission from the train to the fixed station. These comparatively low frequency currents might be transmitted over the metallic circuit and then might teapplied to the longitudinal line sections after being stepped up in frequency. Different frequency'bands might be employed for transmission in opposite directions.

If the energy drain on the amplifier-demodulator apparatus, such as 7, presents a serious problem, it might be desirable to use an. arrangement whereby the power supply of such apparatus is turned on only when the train enters the particular section of the line wherein such apparatus is located. This might be done in conjunction with the apparatus comprising the regular trainautomatic control, or the carrier signaling currentsthemselves might be employed for this purpose, as illustrated in Fig. 2. In this arrangement the longitudinal currents transmitted through winding 5 would be trans' mitted to ground through the input of 'the' demodulator apparatus 7 in the usual manner. Bridgedacross this input circuit would be a rectifier 9 having a relay 10 included in the output circuit thereof. The signaling current thus transmitted to the demodulator would operate the relay 10 to connect a source of energy 11 to the demodulator apparatus 7 to cause it to operate. The output of the demodulator 7 would then apply the incoming currents to the line L metallically rather than longitudinally, asheretofore explained.

By the use of suitable filter circuits the employment of the line circuit may be made selective so that the high frequency carrier currents do not affect the regular telegraph or voice transmission uses of the circuit. If desired, the breaking up of the longitudinal circuit may be carried out by line filter type apparatus at the sectionalizing points, such as illustrated in Fig. 1, by the inductance coils 1 and 2, and the high frequency. circuit may be manipulated independently of the low frequency or voice circuit. It may be desirable either to openup the longitudinal circuit for high frequency while maintaining continuity of the high frequency metallic circuit or to ground the longitudinal circuit or to terminate it in adefinite impedance to ound. In Fig. 3 is shown an arrangement which might be substituted in the line at the sectionalizing points in place of the inductance coils, such as 1. A low-pass filterpartin from the spirit of the invention as define by the appended claims.

What is claimed is:

1. A system for communicating with moving vehicles comprising a transmission line inductively associated with a moving vehicle, means for sectionalizing said line with respect to currents applied thereto in' a certain manner, and means in each of said line sections to apply said currents to said line in a different manner, said sectionalizing means comprising a low-pass filter in said line, a selective circuit bridged around said filter, inductance coils in said bridged circuit hav ing their windings parallel aiding, and means to ground the midpoints of said inductance windings through an impedance.

2. A system for communicating with moving vehicles comprising a transmission line inductively associated with signaling apparatus in a moving vehicle whereby currents will be induced from said signaling apparatus into said line and will traverse the sides of said line in parallel, means for dividing said line into sections with respect to currents traversing the sides of the line in parallel, means for reducing the frequency of currents thus traversing the line, and means for applying said currents as reduced in frequency to said line whereby the; will traverse the sides thereofserially.

3. A high frequency system for counieating with moving vehicles comprising a transmission line inductively associated with signaling apparatus in a moving vehicle, means in said'line for demodulating the currents induced therein from said signaling apparatus, and means for applying said demodulated currents to the sides of said line in series.

a. A high frequency system for communieating with moving vehicles comprising a transmission line inductively associated with signaling apparatus in a moving vehicle,

means for sectionalizing said line with respect to currents induced by said signaling apparatus to traverse the sides of said line in parallel, a circuit individual to each of said line sections and responsive to said induced currents, a demodulator in each of said circuits, means associated with the input of each of said demodulators and responsive to said induced currents for energizing said demod ulator, and means to apply the output current of the demodulator to the sides of the line in series.

5. The method of establishing communication between a transmission line and signaling apparatus in a moving vehicle which comprises causing said signaling apparatus to induce high frequency currents to traverse the sides of said line in an arbitrary manner, sectionalizing said line with respect to said induced currents, reducing the frequency of In testimony whereof, I have signed my name to this specification this 28th day of March 1928.

HERMAN A. AFFEL.

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