WO2009141608A2

WO2009141608A2 - Signs

Info

Publication number: WO2009141608A2
Application number: PCT/GB2009/001269
Authority: WO
Inventors: Michael Cordell; Marcus Boden
Original assignee: E-Plate Limited
Priority date: 2008-05-20
Filing date: 2009-05-20
Publication date: 2009-11-26
Also published as: WO2009141608A3; GB0809145D0; GB2460236A; MX2009003321A; BRPI0903774A2

Abstract

A combination of a sign and a support therefore for attachment to an object, one or both of the sign and support comprising signal generation means and an antenna for receiving and/or broadcasting information, say information about the object, to a location remote from the sign or object, said signal generation means having a first state and a second state, a circuit in operable communication with the signal generation means such that, in use, when the sign or support is attached to the object, the circuit is such that said signal generation means operates or is able to operate in the first state, whereupon removal or partial removal of the sign or support from the object the circuit is such that said signal generation means operates or is able to operate in the second state.

Description

SIGNS

This application relates to signs for attachment to objects and, in particular, to signs which are capable of transmitting information about the object to a location remote from the sign or object.

It is known that many signs are stolen or interfered with by thieves and vandals. For certain signs, e.g. vehicle license plates, safety signs, signs which identify the contents of vehicles and so on, it is essential that they remain located in or on their proper and intended location.

It is an object of this invention to provide a sign which prevents or limits such interference and/or which is capable of indicating interference.

Accordingly, a first aspect of the invention provides a combination of a sign and a support therefore, for attachment to an object receiving and/or broadcasting one or both of the sign and support comprising a signal generation means and an antenna for receiving and/or broadcasting information, say information about the object, to a location remote from the sign or object, the signal generation means having a first state and a second state, a circuit in operable communication with the signal generation means such that, in use, when the sign is attached to the object, the circuit is such that the signal generation means operates or is able to operate in the first state, whereupon removal or partial removal of the sign or support from the object the circuit is such that the signal generation means operates or is able to operate in the second state. Preferably, the sign is a license plate for a vehicle. The license plate may be of any type known in the art, e.g. it may be formed from metal or a plastics material.

Preferably, the object is a vehicle, or part of a vehicle such as a bumper, windscreen or window. The support may be part of the object and is preferably attached or attachable to the object. For example, the support may be a vehicle bumper.

The information may be received and/or broadcast by radio frequency (RF) radiation. The information may pertain to the sign and/or the object to which the sign is attached.

The signal generation means may comprise an RF emitter and/or transmitter, e.g. a radiofrequency identification (RFID) tag.

The signal generation means is preferably "active", or it may be "passive".

Signals may be continuous, interrupted by a predetermined time or intermittent.

The signal generation means may be located within the sign or support, e.g. in a cavity formed therein, or on or attached to a surface of the sign or support. Alternatively, the signal generation means may be provided, for instance, embedded within the body of the sign or support, e.g. in a moulded recess or cavity. The signal generation means is preferably operably connected or connectable to antenna means. Alternatively, the signal generation means may comprise an antenna for transmitting and/or receiving signals.

The circuit may be an electrical circuit, preferably an electrical circuit designed to break, for example physically or operably, at one or more of the locations. The circuit or any part thereof may comprise frangible portions. The circuit or any part thereof may comprise frangible protions.

The electrical circuit may comprise wire seals connected by a wire seal crimp. Preferably, a portion of the wire seal and/or the wire seal crimp will provide one or more specific locations for breaking the electrical circuit.

Preferably, the or a part of the electrical circuit is retained on or within the sign. More preferably, the or a part of the electrical circuit is retained on or within the signal generation means.

The object, to which the sign is attached, in use, may comprise a retaining ring extending outwardly from the surface to which the sign is attached.

The retaining ring may be any suitable size or shape or indeed may be formed from any suitable material. Preferably, the retaining ring is an existing ring already present on the vehicle body. The retaining ring may define an aperture through which a pair of electrically conducting wires may pass.

The sign may further comprise a passage having an open end on each of its major faces through which the pair of electrically conducting wires may pass.

Preferably, the free ends of the electrically conducting wires are connected by a crimp seal to form a complete electrical circuit. It is desirable that the crimp seal is sized and dimensioned so that it cannot enter the passage. Preferably, the crimp seal may be on an opposite face of the sign to the retaining ring.

Alternatively, the circuit may comprise a sensor, for example, for sensing the presence of a material.

Preferably, the sign may comprise a bore, for example a threaded bore, for receiving fixing means, e.g. bolts.

The fixing means may complete the circuit when brought into contact with the bore.

The fixing means may be one or more bolts, the or each having a shaft and a head. The shaft may have a threaded portion. Preferably, the bolt is made from two sections, a first section and a second section. The second section may include the head of the bolt and a portion of the length of the shaft proximal to the head. The first section may include the remaining portion of the shaft.

The first section and the second section may be made from different materials having different physical properties. The sensor may detect a change in state, for example, when the bolt is inserted and/or removed.

For example, the first section of the bolt may be made from a suitable non-conductive material such as a plastics material. The second section of the bolt may be made from a conductive material such as a metal or alloy, for example aluminium, steel, iron, tungsten, titanium, brass or copper. In this example, the circuit is complete when the second section is brought into contact with the bore.

Alternatively, the circuit may comprise an emitter, preferably a reflector, and a detector. The emitter and detector may emit and detect infra red (IR) radiation.

Alternatively, other frequency ranges may be suitable, e.g. microwaves and so on.

Preferably, the emitter and detector may be within close proximity of one another, e.g. built into the same electronic component. More preferably, the emitter and detector may be operably connected to the signal generation means. Alternatively, the emitter and detector may be incorporated within or on the signal generation means.

The emitter and detector may be provided on or within the sign or support and the reflector may be located outboard of the sign or support, e.g. on or within the support for the sign. Alternatively, the reflector may be provided within the sign or support and the emitter and detector may be located outboard of the sign or support, e.g. on or within the support for the sign.

An emitter may be provided on or within one or other of the support and sign and the detector on or within the other. The circuit may be completed by connection means, e.g. wires.

In alternative embodiments of the invention, the emitter and/or detector may be hardwired to the reflector. For example, the emitter may emit a signal via IR to the reflector which, in turn, initiates an electrical signal to transmit from the emitter to the detector via a cable. Equally, the emitter may emit an electrical signal to the reflector via a cable which, in turn, initiates the reflector to transmit an IR signal to the detector.

In these embodiments the "reflector" may not be IR reflective.

Alternatively, use of the reflector may be redundant. For example, the emitter may be provided outboard of the sign, e.g. on or within the support, and the detector may be provided outboard of the support, e.g. on or within the sign.

In this embodiment, the detector may be hardwired to the signal generation means via an electrical cable.

The sign or support may be mounted on a vehicle window or windscreen. Preferably the sign or support may be mounted on the inside of the vehicle window or windscreen.

Preferably, the support may comprise a fixing pad which may be attached, e.g. adhered, to a surface of the window. A reflector, e.g. an IR reflector, may be provided within or on the support, e.g. the fixing pad.

The sign may be fixed to the support, e.g. fixing pad, such that the support may be located between the window and the sign.

Preferably the sign may be adhered less strongly to the support than the support, e.g. fixing pad may be to the object.

Located on or in the signal generation means, e.g. RFID tag, there may be an emitter and a detector, e.g. an IR emitter and detector.

When the sign is fixed to its intended site-of-use the circuit is unbroken, i.e. there is an uninterrupted wave path from the emitter to the detector via the reflector. When there is an uninterrupted wave path the signal generation means may operate in the first state, e.g. it may transmit information indicating that the sign is in its proper and intended location. Alternatively, in the first state there may be no transmission of information from the signal generation means.

Preferably, the IR reflector may be adapted to shatter or become otherwise unusable when an attempt is made to prise the sign from the support. When the sign is fixed to its intended site of use the circuit is unbroken, i.e. there is an uninterrupted wave path from the emitter to the detector via the reflector. When there is an uninterrupted wave path the signal generation means may operate in the first state, e.g. it may transmit information indicating that the sign is in its proper and intended location. Alternatively, in the first state there may be no transmission of information from the signal generation means.

When the sign is removed or partially removed from its intended site of use, e.g. as a result of theft or vandalism, there may not be an uninterrupted wave path from the emitter to the detector via the reflector. When there is an interrupted wave path the signal generation means may operate in the second state, e.g. it may transmit information indicating that the sign is not in its proper and intended location. Alternatively, in the second state there may be no transmission of information from the signal generation means. The support, e.g. fixing pad, may be adapted to shatter or become otherwise unusable when an attempt is made to prise the sign from the support. A second aspect of the invention provides a method of installing a combination of a sign and a support for a sign as described herein which may comprise the steps of: ■ providing a sign and a support therefore;

^■ locating signal generation means in or on one or other of the sign or support; and

^■ completing a circuit when the sign is fixed to the support at an intended site-of-use so as to cause the signal generation means to operate in a first state.

A third aspect of the invention provides a tamper evident signal transmitter for a sign, the transmitter comprising signal generation means and an antenna to transmit a signal generated thereby, and also comprising a radiation emission means and radiation detection means, the emission means and detection means being operable to cause said signal generation means to operate in a first state and operable to cause said signal generation means to operate in a second state after the signal transmitter or a sign with which it is associated has been tampered with.

The terms first state and second state as used in this application mean or refer to the type, strength or content of the signal transmitted by the signal generation means. It will be appreciated that the type, strength or content of the signal will differ between the first state and the second state. The term support in this application may refer to housing for a sign, e.g. a licence plate holder, or a support to which a sign is secured, e.g. a vehicle bumper.

In order that the invention may be more fully understood, it will now be described, by way of example only and with reference to the accompanying drawings, in which:

Figure 1 shows a first embodiment of a combination according to the invention;

Figure 2 shows a second embodiment of a combination according to the invention;

Figure 3 is a perspective view of the disassembled components of a third embodiment of a combination according to the invention;

Figure 4 is a perspective view of an assembly of the components shown in Figure 3;

Figure 5 is a perspective view of the disassembled components of a fourth embodiment of a combination according to the invention;

Figure 6 is a perspective view of an assembly of the components shown in Figure 5. Figure 7 shows a further specific embodiment of a combination according to the invention.

Referring to Figure 1, there is shown in cross-section a portion of a vehicle body 10, e.g. a bumper, and a vehicle license plate 11. The body 10 has an outer surface 10a, secured to which is a retaining ring 12.

The retaining ring 12 and the outer surface 10a of the body 10 define an aperture 17, the long sides of which are substantially parallel with the outer surface 10a of the body 10.

The plate 11 has a first major surface 11a and a second major surface lib. The plate 11 has a radio frequency identification (RFID), tag 14 located between the first major surface 11a and the second major surface lib.

An antenna (not shown) for transmitting and/or receiving signals is operably connected to the RFID tag 14.

A pair of electrically conducting wires 13 extend from connection points 16 on the RFID tag 14. The wires extend from the RFID tag 14, through the body of the plate 11 and emerge from the second major surface lib to leave two free lengths of wire 13. The plate 11 also comprises a passage which passes through the thickness of the plate 11 from the first major surface 11a to the second major surface lib. As shown in Figure 1, in use, the second major surface lib of the plate 11 typically faces the outer surface 10a of the body 10. The plate 11 may be mounted to the body 10, e.g. a bumper, by any suitable method.

In order to realise the benefits of the invention during installation of the plate 11, the free lengths of wire 13 are first passed through the aperture 17 and then passed through the passage in the plate 11 so that the unconnected ends of the free lengths of wire 13 emerge from the first major surface 11a of the plate 11.

A wire seal crimp 15 is then used to fasten the free lengths of wire 13 to one another at a location outside the plate and proximal to the first major surface 11a of the plate 11, thereby generating a completed electrical circuit which includes the RFID tag 14. The crimp 15 is sized and dimensioned such that it cannot pass through the passage in the plate 11.

When the electrical circuit is complete, the RFID tag 14 adopts a first or "fitted" state.

When an unscrupulous person attempts to remove the plate 11 from the vehicle body 10, the wire 13 and/or the crimp 15 will break. Consequently, the electrical circuit to the RFID tag 14 is broken. When the electrical circuit is broken, the RFID tag 14 adopts a second or "tamper" state. For example, it may cease to transmit information or it may commence transmission of information or it may transmit different information from that transmitted in the first state.

As will be appreciated, in these embodiments the portion of a vehicle body 10,20, e.g. a bumper, provided the support for the sign, the vehicle (not shown) being the object to which the combination is attachable.

Referring now to Figure 2 there is shown a second embodiment of the invention. Figure 2 shows in cross-section a portion of a vehicle body 20, with an outer surface 20a to which is attached a vehicle license plate 21.

The plate 21 has a first major surface 21a and a second major surface 21b. The radio frequency identification (RFID) tag 22 is located between the first major surface 21a and the second major surface 21b of the plate 21.

The RFID tag 22 comprises a sensor (not shown).

A first bore passes through the plate 21 from the first major surface 21a to the second major surface 21b at a location remote from the RFID tag.

A second bore passes through the plate 21 from the first major surface 21a to the second major surface 21b in a region where the sensor is located on the RFID tag. The plate 21 is mounted to the vehicle body 20 by fixing means comprising at least in part a first bolt 23 and a second bolt 24. The first bolt 23 and second bolt 24 each comprise a head and a shaft. The shafts of the first bolt 23 and second bolt 24 comprise threaded portions which may engage a nut (not shown).

The first bolt 23 extends through the first bore before entering the vehicle body 20 so as to fix the plate 21 to the vehicle body 20 using the nut.

The second bolt 24 extends through the second bore before entering the vehicle body 20 so as to fix the plate 21 to the vehicle body 20 using a nut.

The second bolt 24 when located within the second bore operably engages the sensor contained within the RFID tag 22.

The second bolt 24 is shown in more detail in the exploded view A of Figure 2. The second bolt 24 comprises two sections: a first section 25 and a second section 26. The second section 26 includes the head of the bolt and a portion of the length of the shaft proximal to the head. The first section 25 includes the remaining portion of the shaft.

The first section 25 is made from a non-conductive plastics material. The second section 26 is made from a conductive material, typically a metal or alloy. When the bolt 24 in the second bore the bolt 24 is detected by the sensor of the RFID tag 22. As the bolt 24 is introduced the first bolt section 25 is detected by the sensor. When the second bolt section 26 is in place the second bolt section 26 is detected by the sensor and the RFID tag 22 adopts a first "fitted" state.

When an unscrupulous person attempts to remove the plate 21 from the vehicle body 20, the bolts 23, 24 need to be undone. As the second bolt 24 is being removed from the second bore, the first bolt section 25 of the second bolt 24 will be detected by the sensor. The change in material detected by the sensor causes the RFID tag 22 to adopt a second or "tamper" state.

Referring now to Figure 3 there is shown a perspective view of the disassembled components of an alternative embodiment of the invention. Figure 3 shows a portion of a vehicle body 30, e.g. a bumper, a vehicle license plate 31, an RFID tag 32, a housing 33 for the RFID tag 32, a infra red reflective panel 34 and a support 35 and a plurality of bolts 36.

The portion of a vehicle body 30 has an outer surface 30a.

The vehicle license plate 31 is a metallic, e.g. aluminium or steel, plate. The plate 31 has a first major surface 31a, which bears indicia 38 and a second major surface 31b. Spaced at intervals and close to the perimeter of the plate 31 are apertures 39 for receiving fixing means, e.g. bolts 36. The support 35 has a first major surface 35a and a second major surface 35b. The support is made from a material which is permeable to radio waves and infra red wavelength radiation, a plastics material, e.g. acrylic, may be preferred. The first major surface 35a of the support 35 has substantially the same dimensions as the second major surface 31b of the sign 31 except that it has an additional lip portion 40 on its bottom edge.

The RFID tag 32 comprises a body 321 having attached thereto signal generation means 322 and an antenna 323. The body 321 further comprises an infra red emitter (not shown) and an infra red detector (not shown).

The housing 33 comprises a rebate defined by a base and an upstanding peripheral wall 37.

The infra red reflective panel 34 is a relatively thin panel made from a material that reflects infra red radiation.

Referring now to Figure 4, there is shown a perspective view of an assembly of the components shown in Figure 3.

The assembly shown in Figure 4 may be put together as follows.

The housing 33 is affixed to the surface 30a of the portion of the vehicle body 30 such that the peripheral wall 37 of the housing 33 defines a rebate in which the RFID tag 32 is located. The second major surface 35b of the support 35 is attached to the surface 30a of the body 30 so as to cover the RFID tag 32 and housing 33. Alternatively, the RFID tag 32 and housing 33 may be concealed within a cavity in the second major surface 35b of the support 35.

The antenna 323 is positioned directly behind the lip portion 40 of the support 35.

The IR reflective panel 34 is located between the support 35 and the licence plate 31. The panel 34 is preferably affixed, e.g. using adhesive, to the second major surface 31b of the plate 31. The plate 31 is fixed to the support 35 by screws 36 passing through apertures 39 such that the indicia 38 are visible on the front of the assembly.

As can be seen from Figure 4, the lip portion 40 and hence the antenna 323 is not obscured by the plate 31. This allows radio frequency transmissions to be emitted/detected from the front of the assembly. As will be appreciated, the metal plate 31 would reflect or at least attenuates radio waves if the antenna 323 was obscured by the plate 31.

Located between the second major surface 35b of the substrate 35 and the outer surface 30a of the body 30 is the RFID tag 32. The RFID tag 32 fits snugly within the housing means 33 to ensure that when in use, e.g. attached to a moving vehicle, the antenna 323 of the tag 32 remains in line with the reflective panel 34 such that infra red radiation transmitted by the tag 32 can be reflected by the panel 34 back to the infra red receiver on the tag 32.

When the circuit is unbroken, i.e. complete, the RFID tag 32 adopts a first or "fitted" state.

When an unscrupulous person removes the plate 31 from the vehicle body 30, the reflective panel 34 will no longer reflect the transmitted IR signal to the IR receiver of the RFID tag 32, in effect, breaking the circuit,

When the circuit is broken, i.e. incomplete, the RFID tag 32 is caused to operate in a second or "tamper" state.

Referring now to Figure 5 there is now shown a perspective view of the disassembled components of a further embodiment of the present invention.

Figure 5 shows a portion of a vehicle windscreen 50, a fixing pad 51 and an RFID tag 52. The RFID tag 52 may display indicia and/or other markings.

The vehicle windscreen 50 is substantially planar and has a first major surface 50a and a second major surface 50b. The fixing pad 51 is substantially planar and has first 51a and second 51b major surfaces. The pad 51 in this embodiment of the invention is a High Bond Pad.

Located within the pad 51 is a reflective IR panel 53. The pad 51 is made from an ultra destruct material and once fitted it cannot be removed without breaking into many fragments. If the pad 51 breaks the reflective panel 53 will no longer operate.

The RFID tag 52 corresponds to the shape of the fixing pad 51. The tag 52 has first 52a and second 52b major surfaces. The tag 52 transmits and receives data via IR.

Figure 6 is a perspective view of the assembled components of the embodiment as shown in Figure 5, wherein the RFID tag 52 is secured to a major surface 50a of a vehicle windscreen by means of a fixing pad 51. Located within the pad 51 is a reflective IR panel (not shown).

The second major surface 51b of the pad 51 comprising the reflective panel 53 is secured to the first major surface 50a of the windscreen 50. To the first major surface 51a of the pad 51 is secured the second major surface 52b of the tag 52.

In use, the RFID tag 52 transmits data via an IR transmitter (not shown) which is reflected back to an IR receiver (not shown) by the reflective panel 53, effectively completing a circuit. When the circuit is unbroken, i.e. complete, the RFID tag 52 adopts a first or "fitted" state.

When an unscrupulous person tampers with the identification tag 52, e.g. prises the tag 52 from the pad 51 or prises the pad 51 from the windscreen 50, the reflective panel 34 no longer reflects the IR signal transmitted by the tag 52, which effectively breaks the circuit.

When the circuit is broken, i.e. incomplete, the RFID tag 52 adopts a second or "tamper" state.

Figure 7 shows in cross-section an alternative embodiment of the invention. Figure 7 shows a support 60, a sign 61, e.g. an identification plate, an IR reflector 62 and an RFID tag 63.

The support 60, which may be attached to a part of a vehicle body, comprises a first surface 60a and a second surface 60b. The second surface 60b stands proud of the first surface 60a. The RFID tag 63 is located on or within the support 60.

The tag 63 comprises an IR transmitter and receiver 63a, signal generation means 63b and an antenna 63c.

The IR transmitter and receiver 63a and the signal generation means 63b are located on or within a region adjacent the first surface 60a of the support 60. The antenna 63c is located on or within a region adjacent the second surface 60b of the support 60.

Connection means 63d connect the signal generation means 63b to the antenna 63c.

The reflector 62 is fixed to a major surface 61a of the sign 61. The reflector 62 is made from a material that reflects infra red radiation.

In this embodiment of the invention the sign 61 is metallic, e.g. made from aluminium or steel.

When assembled, the major surface 61a of the sign 61 is fitted to the first surface 60a of the support 60.

Therefore, in use, the IR transmitter 63a transmits a signal which is reflected to the IR receiver 63a via the reflector 62 thus completing a circuit. The signal generation means 63b generates a signal which passes along the connection means 63d to the antenna 63c.

The signal transmits from the antenna 63c to a location remote from the sign or support. When the circuit is unbroken the tag 63 adopts a first or "active" state.

Because the antenna 63c is located outboard of the signal generation means 63d in a region away from the metallic sign 61, it will be appreciated that the signal will transmit from the antenna 63c without interference from the sign 61.

If the sign 61 is removed from the support 60 the IR reflector will no longer reflect the IR radiation and the circuit will break.

When the circuit is broken the tag 63 adopts a second or "tamper" state.

It is to be appreciated that the invention may differ from that described in the specific description without departing from the overall scope of the invention. For example, electronic components such as the emitter and/or detector and/or reflector and/or signal generation means may be hardwired to one another.

It is to be appreciated that the invention may provide a combination of a sign and a support therefor, for attachment to an object, one or both of the sign and support comprising a signal generation means for transmitting information, say information about the object, to a location remote from the sign or object, the signal generation means having a first state and a second state, a circuit in operable communication with the signal generation means such that, in use, when the sign is attached to the object, the circuit causes the signal generation means to operate in the first state, whereupon removal or partial removal of the sign or support from the object the circuit causes the signal generation means to operate in the second state.

Claims

1. A combination of a sign and a support therefore for attachment to an object, one or both of the sign and support comprising signal generation means and an antenna for receiving and/or broadcasting information, say information about the object, to a location remote from the sign or object, said signal generation means having a first state and a second state, a circuit in operable communication with the signal generation means such that, in use, when the sign or support is attached to the object, the circuit is such that said signal generation means operates or is able to operate in the first state, whereupon removal or partial removal of the sign or support from the object the circuit is such that said signal generation means operates or is able to operate in the second state.

2. A combination according to Claim 1, wherein the circuit comprises an emitter and a detector.

3. A combination according to Claim 2, wherein the emitter and/or detector emit and/or detect infra red (IR) radiation.

4. A combination according to Claim 2 or Claim 3, wherein the circuit comprises a reflector.

5. A combination according to Claim 4, wherein the emitter and detector are provided on or within said sign or support and the reflector is provided outboard of said sign or support.

6. A combination according to Claim 4, wherein the reflector is provided on or within said sign or support and the emitter and detector are provided outboard of said sign and support.

7. A combination according to Claim 2 or Claim 3, wherein the emitter is provided on or within one or the other of the support or the sign and the detector is provided on or within the other.

8. A combination according to Claim 1, wherein the circuit is an electrical circuit.

9. A combination according to Claim 8, wherein the electrical circuit comprises frangible portions.

10. A combination according to Claim 9, wherein the frangible portion is a wire seal crimp.

11. A combination according to Claim 8, wherein the circuit comprises a sensor for sensing the presence of a material.

12. A combination according to Claim 11, wherein the sensor is located on or within said sign or support so as to detect fixing means.

13. A combination according to Claim 12, wherein said fixing means are one or more bolts.

14. A combination according to Claim 12 or Claim 13, wherein said fixing means comprise two sections: a first section and second section.

15. A combination according to Claim 14, wherein said first and second sections are made from different materials having different physical properties.

16. A combination according to Claim 14 or Claim 15, wherein said first section is made from a suitable non-conductive material and said second section is made from a suitable conductive material.

17. A combination according to Claim 15 or Claim 16, wherein the difference in material causes a change in said state of said signal generation means.

18. A combination according to any preceding Claim, wherein said signal generation means comprises a radio frequency (RF) transmitter and/or receiver.

19. A combination according to any preceding Claim, wherein said signal generation means is located on or within said sign or support.

20. A combination according to any preceding Claim, wherein the sign is a license plate for a vehicle.

21. A method of installing a combination of a sign and a support for a sign comprising the steps of:

^■ providing a sign and a support therefore;

^■ locating signal generation means operable in a first and second state in or on one or other of the sign or support; and

^■ completing a circuit when the sign is fixed to the support at an intended site-of-use so as to cause said signal generation means to operate in a first state.

22. A tamper evident signal transmitter for a sign, the transmitter comprising signal generation means and an antenna to transmit a signal generated thereby, and also comprising a radiation emission means and radiation detection means, the emission means and detection means being operable to cause said signal generation means to operate in a first state and operable to cause said signal generation means to operate in a second state after the signal transmitter or a sign with which it is associated has been tampered with.