# Patent

## Title
Railway circuit for sending signalling information along a railway line to a vehicle travelling along the railway line

## Abstract

A railway circuit for detecting the free or occupied state of the same and for sending signalling information along a railway line to a vehicle travelling along said railway line. A signal generator generates a signal with varying current modulated with FSK technique on a basis of a modulation code. The signal is supplied to a coil magnetically coupled with first and second rails that constitute the single railway circuit to induce a variable current modulated by the code on the electric circuit formed by the portions of the first and second rail short-circuited alternatively by the electric joint. The vehicle is provided with a current sensor suitable for detecting the variable current for extraction of the code and sending the signal to the driver. A signal generator generates a signal in compliance with new safety requirements to determine, with the receiver, the free/occupied state of the railway circuit.

## Background
TECHNICAL FIELD
At least one embodiment of the present invention concerns a railway circuit suitable for sending signalling information along a railway line to a vehicle travelling along the railway line.
BACKGROUND
Railway circuits are known for detecting the presence of a vehicle travelling along the railway line comprising:
a first signal generator suitable for generating an alternating signal V(t) with varying voltage supplied to a first conductor which comprises rectilinear sections arranged adjacent to respective portions of a first and a second rail to define at least a first square coil magnetically coupled with the first and the second rail;
a signal receiver suitable for receiving the alternating signal V(t) present on the railway by means of a second square coil comprising a second conductor which comprises rectilinear sections arranged adjacent to respective portions of the first and second rail and magnetically coupled to the rails; the signal receiver is suitable for discriminating between two states:
a condition of signal received above a threshold in which the rails are not short-circuited by an axle of the vehicle and the railway circuit is considered free; and
a condition of signal received below a threshold or null in which the rails are short-circuited by at least one axle of a railway vehicle present on the railway and the railway circuit is considered occupied.
A railway circuit of the type described above can be—for example—equipped using the devices P-1400 of the company Railroad Control Limited in accordance with U.S. Pat. Nos. 5,936,551; 6,087,964; 6,226,575; and 6,281,809.
SUMMARY
The object of at least one embodiment of the present invention is to use a railway circuit of the type described above or analogous for the transmission of further information along the railway line.
The above object is achieved by at least one embodiment of the present invention which relates to a railway circuit suitable for sending signalling information along a railway line to a vehicle travelling along the railway line comprising:
first signal generator means suitable for generating an alternating signal V(t) with varying voltage supplied to a first conductor which comprises sections arranged adjacent to and within respective portions of a first and a second rail facing towards the inside and belonging to a railway circuit to define at least a first coil magnetically coupled with the first and the second rail;
signal receiver means suitable for receiving said alternating signal V(t) present on said railway circuit by means of a second coil in which a second conductor comprises sections arranged adjacent to respective portions of the first and second rail and magnetically coupled with said rails; the signal receiver means being suitable for detecting a condition of signal received null or below a threshold when said rails are short-circuited by at least one axle of a railway vehicle present on said railway circuit, characterised in that it comprises second signal generator means suitable for generating a signal I(t) with varying current on the basis of a modulation code (CODE) associated with said signalling information; said signal I(t) being supplied to a third conductor which comprises sections arranged adjacent to respective portions of the first and second rail facing towards the outside to define at least a third coil coaxial and external to the first and magnetically coupled with the first and second rail; said second signal generator means being suitable for inducing on the electric circuit formed by the portions of the first and second rail short-circuited by said axle a variable current Iab(t) modulated by said code; said railway vehicle being provided with current detector means suitable for detecting said variable current Iab(t) for extraction of said code (CODE) and sending of said signalling information.



BRIEF DESCRIPTION OF THE DRAWING
The invention will be illustrated with reference to the attached drawing which represents—in a schematic manner—a non-limiting embodiment.



DETAILED DESCRIPTION
In the attached FIGURE the number 1 indicates, as a whole, a railway circuit for sending signals along a railway line 3 to a vehicle 2 (illustrated schematically—for example an electric locomotive) travelling along the railway line 3.
The railway line 3 comprises a plurality of pairs of rails 5a,5b electrically connected to one another by means of respective electrical joints (of known type); consecutive pairs of rails (each pair of rails defines a respective railway circuit) are functionally separated from one another by the electrical joint.
The railway circuit 1 comprises:
a first signal generator 6 (of known type) suitable for generating an alternating signal V(t) (typically a signal with frequency in the range 3.5+16.5 kHz and voltage in the maximum range of 10 Veff) with varying voltage supplied to a first conductor 7 which comprises rectilinear sections 7a, 7b arranged adjacent to respective first end portions of the first and second rail 5a, 5b facing towards the inside to define at least a first square coil 8 magnetically coupled with the first and the second rail 5a,5b; and
a signal receiver 9 suitable for receiving the alternating signal V(t) present on the rail by means of a second square coil 10 comprising a second conductor 11 which comprises rectilinear sections 11a, 11b arranged adjacent to respective second end portions of the first and second rail 5a, 5b and magnetically coupled with the rails 5a,5b. 
The rectilinear sections 7a, 7b and 11a, 11b are arranged adjacent to respective internal facing portions of the rails 5a, 5b so that the track of the square coils 8 and 10 lies within the area delimited by the tracks of the rails 5a, 5b. 
The signal receiver 9 is suitable for discriminating between two states:
a condition of signal received above a threshold in which the rails 5a, 5b are not short-circuited by an axle of the vehicle and the railway circuit is considered free (i.e. no vehicle is present);
a condition of signal received below a threshold or null in which the rails 5a, 5b are short-circuited by at least one metallic axle 12 of the railway vehicle 2 and the railway circuit is considered occupied.
According to an embodiment of the present invention, the railway circuit 1 comprises a second signal generator 13 (also of known type and illustrated schematically) suitable for generating a signal I(t) with varying current on the basis of a modulation code CODE associated with a signal to be transmitted to the vehicle 2. Typically the signal relates to the state of the railway circuits subsequent to the one in which the vehicle 2 is located.
The signal I(t) is supplied to a third conductor 14 which comprises rectilinear sections 14a, 14b arranged adjacent and external to respective portions of the first and second rail 5a, 5b to define at least a third coil 15 coaxial to the first coil 8 (the track of the axle is indicated by 16) and magnetically couple with the first and the second rail 5a,5b. 
The second signal generator 13 is suitable for inducing on the electric circuit formed by the portions of the first and second rail 5a, 5b (said portions are indicated by the dot and dash line), short-circuited by the axle 12, a variable current Iab(t) modulated by the code CODE.
The railway vehicle 2 is provided with at least one current sensor 17 suitable for detecting the variable current Iab(t) and emitting an output signal which is sent to an electronic control unit 19 (shown schematically) present on the railway vehicle 2 and used for extraction of the code CODE and supply of the relative signal to the driver (not illustrated) of the railway vehicle.
The rectilinear sections 14a, 14b are arranged adjacent to respective opposite external portions of the rails 5a, 5b so that the track of the square coil 15 overshoots the area delimited by the tracks of the rails 5a,5b. 
Consequently, in plan view, the first coil 8 is internal with respect to the third coil 15 and the rail 5a (5b) is interposed respectively between the rectilinear section 14a (14b) of said first coil 8 and the rectilinear section 7a (7b) of said coil 15. This arrangement (the sections 14a/7a and 14b/7b are arranged on opposite sides of the respective rails 5a, 5b alongside which they are positioned) introduces an effective magnetic shielding between the first coil 8 which is internal with respect to the third external coil 15 and allows the independent operation of these two coils, minimising the magnetic coupling.
Expediently, the third coil 15 can be provided on railway circuits which already have the first coil 8 and the second coil 10 so as to integrate an existing railway circuit with new functions to, thus, allow updating of a railway line to new safety requirements which entail the transmission of a code, maintaining unchanged the installations and equipment on board the railway vehicle which operate with the existing railway circuits.
Moreover the second signal generator 13 is suitable for modulating the signal I(t) by means of Frequency-Shift-Keying technology. The frequency of the signal I(t) is different from the frequency of the signal V(t).
As is known, frequency-shift keying (FSK) is a numerical frequency modulation technique or scheme, in which the modulating signal containing information (in this case the bits of the CODE code) shifts the frequency of the output carrier from one to another of two pre-determined frequency values.
On the basis of the above, the following architecture is created:
the coil 15 is arranged on the outside of the perimeter of the first coil 8 with the rectilinear sections 14a, 14b facing the outer side of the rails 5a, 5b and the rectilinear sections 7a, 7b facing the inner side of the rails 5a, 5b. 
On the basis of the tests performed by the inventors, said arrangement minimises the interferences between the coils 8 and 15 and ensures that the operation of each of the two coils in question (used for performing distinct independent safety functions) does not substantially influence that of the other, also in the event of failures on one of the two coils.
The railway circuit could have a fourth coil (not illustrated) with analogous structure and function to that of the third coil 15 and therefore supplied by a signal generator analogous to the signal generator 13. Said fourth coil would be coaxial to the second coil 10 providing a symmetrical system for the transmission of data to the vehicle 2 independently of its direction of forward movement, since the third coil 15 and the fourth coil would be used with the function of transmission and reception respectively (or vice versa) according to the direction of movement of the vehicle 2.
In the event of the railway circuit being free, the third and fourth coil could be used respectively for transmission (reception) and reception (transmission) of the signal I(t) in order to test the railway circuit and all the connections relative to said third and fourth coils and relative transmission and reception systems.

## Claims

1. A railway circuit for sending signalling information along a railway line to a vehicle travelling along the railway line, the railway circuit comprising:
first signal generator means suitable for generating an alternating signal with a varying voltage supplied to a first conductor that comprises sections arranged adjacent to and within respective portions of a first and a second rail facing towards the inside and belonging to a railway circuit to define at least an inner first coil magnetically coupled with the first and the second rail;
signal receiver means suitable for receiving said alternating signal present on said railway circuit by means of a second coil, wherein a second conductor comprises sections arranged adjacent to respective inner portions of the first and second rail and magnetically coupled with said rails, the signal receiver means being suitable to detect a condition of signal received null or below a threshold when said rails are short-circuited by at least one axle of a railway vehicle present on said railway circuit; and
second signal generator means suitable for generating a signal with variable current on the basis of a modulation code associated with said signalling information; said signal being supplied to a third conductor which comprises sections arranged adjacent to respective outer portions of the first and the second rail facing towards the outside to define at least an outer third coil coaxial and external to the inner first coil and magnetically coupled with the first and the second rail;
wherein said second signal generator means being suitable to induce on the electric circuit, formed by the portions of the first and the second rail short-circuited by said axle, a variable current modulated by said code; said railway vehicle being provided with current detector means suitable for detecting said variable current for extraction of said code and sending of said signalling information.

2. The railway circuit as claimed in claim 1, wherein said second signal generators are suitable for modulating said signal by means of Frequency-Shift-Keying technology.

3. The railway circuit as claimed in claim 1, wherein, in plan view, said third coil is external to said first coil.

4. The railway circuit as claimed in claim 1, wherein said first and said third coil have in plan view a rectangular perimeter.

5. The railway circuit as claimed in claim 1, wherein said second coil has in plan view a rectangular perimeter.

6. The railway circuit as claimed in claim 1 wherein, in plan view, the sections of said first coil are internal with respect to the sections of rail of the railway circuit.

7. The railway circuit as claimed in claim 1 wherein, in plan view, the sections of said third coil are external with respect to the sections of rail of the railway circuit.