GB2408498A - Cable displacement mechanism for an electronic surveillance device - Google Patents

Abstract

A cable displacement mechanism 10 for an electronic surveillance device comprises a base unit 15 housing a cable storage mechanism, a remote unit housing a transducer (not shown) and a telescopic arm 11 within which passes an electrical cable 12 linking the base unit and the remote unit. The telescopic arm may comprise a plurality of hollow coaxial sections 1,2, each of which is at least partially retractable into the base unit. The cable storage mechanism may apply a tension to the cable passing through the telescopic arm and may comprise a support structure which supports the cable within the base unit parallel to the telescopic arm. The remote unit may be a transducer head. In use, the cable displacement mechanism allows the transducer to be used to be positioned at as range of extension lengths from the base unit, so as to reach into relatively inaccessible places, whilst protecting the electrical cable from harm.

Description

CABLE DISPLACEMENT MECHANISM

The present invention relates to cable storage devices, and in particular to apparatus for allowing a variable distance between one electrical component (e.g. a transducer unit) and another electrical unit (e.g. a main control and/or signal processing unit), using a fixed length of interconnection cable.

In particular, though not exclusively, the invention relates to countersurveillance devices including counter-surveillance electronic device detectors used in the detection of radiating and/or non-radiating electronic eavesdropping devices. Such counter-surveillance devices conventionally have a transducer head on a 'flying lead' coupled to a base unit housing the detection, control and signal processing circuitry.

When performing Technical Surveillance Counter Measures investigations an operator will normally try to position a detector transducer head over areas which may offer potential for eavesdropping device concealment.

Many of the areas searched will include relatively inaccessible places, such as high up on or behind walls and ceilings etc. Hence, it is commonplace to incorporate within such counter-surveillance devices a suitable mechanism for extending the detector transducer head to variable distances remote from a main control / processing unit, hereinafter 'base unit'.

In the prior art, various techniques have been deployed to allow for such variable positioning of the detector transducer head relative to the base unit.

By way of example, one prior art method is to connect the transducer unit to the main control / processing unit via a fixed length of exposed cable. This method inconveniently results in a trailing length of cable which can be as long as the maximum required extension distance between the transducer head and the base unit.

The exposed cable can potentially catch on various items within the search area (e.g. office furniture), damaging the cable or said items. In the worst case, the cable can cause potential safety hazards.

Furthermore, such methods usually include bulky catch mechanisms for setting the extension distance for the transducer head. The catch mechanisms can add undesirable weight and make the detector more cumbersome.

By way of further example, another prior art technique utilises a cable winding mechanism whereby excess cable is wrapped around the transducer 1 5 unit.

Such methods still require the bulky catch mechanisms and still offer exposed areas of interconnect cable which under certain circumstances can result in cable damage.

Counter-surveillance devices inherently need to be sensitive instruments in order to fulfil their design task, and mechanical or physical damage to the cable extending between the base unit and the transducer head is undesirable, not least because it may affect the electrical characteristics thereof.

Thus, a need exists for a mechanism which can allow the transducer head to be easily and safely positioned at a range of extension lengths from the base unit preferably whilst partially or fully protecting the cable from potential damage when in an extended and/or retracted condition.

It is an object of the present invention to overcome some or all of the above disadvantages.

The present invention provides a mechanism for extending and retracting the transducer head of an electronic eavesdropping device detector while providing cable protection.

According to one aspect, the present invention provides a cable displacement mechanism for an electronic surveillance device detector comprising: a base unit housing a cable storage mechanism; a remote unit for housing at least one transducer for transmitting and/or receiving electromagnetic radiation; and a telescopic arm extending between the base unit and the remote unit, the telescopic arm having an electrical cable extending therethrough for electrically connecting the base unit and the remote unit.

Embodiments of the present invention will now be described by way of example and with reference to the accompanying drawings in which: Figure 1 is a partial perspective view of a cable displacement mechanism in a retracted configuration; Figure 2 is a partial perspective view of the cable displacement mechanism of figure 1 in an extended configuration; Figure 3 is a detailed cross-sectional side view of the cable displacement mechanism of figures I and 2; and Figure 4 is a detailed cross-sectional plan view of the cable displacement mechanism of figures 1 and 2.

Referring to Figure 1, a cable displacement mechanism 10 according to a preferred embodiment of the present invention comprises a telescopic arm or monopod 1 1 which is extendable out of, and retractable into, a base unit 15 (shown in dashed outline only) of an electronic surveillance device detector.

The telescopic arm 11 includes a plurality of coaxial sections 1, 2 which are longitudinally displaceable relative to one another to expand and contract a longitudinal dimension of the arm, according to known principles.

The mechanism 10 also includes: a cable storage mechanism 3 adapted to support a predetermined length of electrical cable 12; a control foil 4 for controlling and guiding the extension and retraction of the telescopic arm; and a rear guide mechanism 5 for guiding the electrical cable into and out of the coaxial sections 1, 2 of the telescopic arm 1 1.

A pair of flange plates 6, 7 provide a supporting structure for connection to a wall 16 of the base unit 15 housing (shown in outline only). Preferably, the outer flange plate 6 provides a part of, or is integrated into, a wall of the base unit housing. Alternatively, the flange plates 6, 7 may sandwich a wall 16 of the base unit 15 housing.

The telescopic arm sections 1, 2 are used to connect a transducer head housing (not shown) to the base unit 15. The transducer head housing preferably includes electromagnetic transducers suitable for transmitting and/or receiving electromagnetic radiation for the detection of radiating and/or non-radiating eavesdropping devices. The base unit 15 typically houses signal processing circuitry, a power supply or power supply interface, user interfaces such as keypads, displays and audio outputs. The transducer head may also house limited signal processing circuitry such as pre-amplifiers and the like.

The telescopic arm sections 1, 2 are preferably hollow such that they can be used to completely conceal and protect an electrical cable 12 that enables electrical communication between the transducers in the transducer head and the signal processing circuitry in the base unit 15.

The electrical cable 12 preferably comprises a number of electrical conductors for communication with multiple transducers in the transducer head. The cable l 2 may provide the electrical conductors within a common sheath (e.g. a multi-core cable) or multiple separate cables may be used.

The control foil 4 is used in conjunction with the rear guide mechanism 5 to control the extension and retraction of the telescopic arm sections 1, 2. The control foil preferably comprises a metal strip of curved section to provide sufficient strength in compression and tension to provide push and pull forces on the first (inner) telescopic arm section l as will become clear later.

With reference to figures 3 and 4, a first end 4A of the control foil 4 is attached to the second flange plate 7 and a second end 4C of the control foil is attached to an inner bush 8 which is connected to and forms the proximal end of the inner telescopic arm section 1. The control foil also passes through rollers 4B in the rear guide mechanism 5. The rear guide mechanism 5 includes a bush 5A which is attached to the second (outer) telescopic arm section 2.

The control foil 4 and the rear guide mechanism S are preferably used to maintain a constant tension on the cable 12 on cable storage mechanism 3 as the telescopic arm sections 1, 2 are extended and retracted.

The cables 12 are anchored or attached to the flange plate 7 as shown at position 3A. With a predetermined level of tension, the cables 12 pass s around the rear guide mechanism 5 at position 3B, into the second (outer) telescopic arm section 2 and then into the first (inner) telescopic arm section 1 through the bushing 8 at position 3C. The cables 12 pass through the first telescopic arm section 1 to a distal end at 3D where they are connected to a transducer head (not shown).

In principle, it will be seen that the cable tension is maintained by varying the position of guide mechanism 5 (a support structure around which the cable passes) relative to the cable anchorage position 3A and the (varying) position of the cable anchorage 3C at bushing 8. The cable is preferably clamped at anchorage 3C, although alternatively, the cable could be clamped instead at the distal end 3D of the inner telescopic arm section, or any position in between.

A friction catch 9 is provided to provide a closing detent to the telescopic sections 1 and 2.

In use, as the telescopic arm is pulled out of the housing 15 (e.g. by pulling on the transducer head housing), movement of one of the inner telescopic section 1 and the outer telescopic section 2 is communicated to the other by way of the control foil 4. For example, if the inner section is pulled, the control foil is pulled with it and runs through rollers 4B in the rear guide mechanism 5. This pulls the rear guide, and the outer telescopic section 2 to which it is attached. Conversely, if the outer telescopic section 2 is pulled out of the housing 15, the control foil 4 then pushes the inner section l out of the second section 2. In this manner, the first and second sections l and 2 extend simultaneously and substantially equally to one another. (In other words, the inner section 1 extends out of the outer section 2 at a rate substantially the same as the rate at which the outer section emerges from the housing 15.

At the same time, the cables 12 are pulled, by the inner bush 8, around the rear guide bush 5A from inside the base unit or cable displacement mechanism housing (shown in dashed outline) into the outer telescopic arm section 2. In the reverse operation, as the telescopic arm is slid back into the housing, the outer section pulls on the foil 4 via the rear guide bush 5A and thus pulls inner section 1 into outer section 2.

In the preferred arrangement described, the cable tension remains substantially constant with the telescopic arm fully extended, fully retracted or any position in between.

By housing the cable within the telescopic sections, risk of damage to the cable in normal use is eliminated or substantially reduced.

The flange plates 6, 7 are used to anchor the cable storage mechanism 3 and control foil 4 within the base unit and are also used as a guide for the telescopic arm sections 1, 2 as they are extended and retracted out of and into the base unit 15.

The cable storage mechanism 3 and the control foil 4 are also anchored to the base of the outermost telescopic arm section 2.

Although the cable displacement mechanism 10 is shown in the drawings as having just two telescopic arm sections 1, 2, it will be understood that any suitable number may be used to provide a desired extension length. Suitable modifications could then be made to provide a cable displacement mechanism which stores and tensions an appropriate length of cable.

Although the telescopic arm sections 1, 2 are shown in the drawings as being of hollow circular cross-section, it will be understood that other cross- sectional profiles (e.g. rectangular) may be used. The cross-section may also be solid rather than hollow, with the cable 12 residing against an outer surface thereof, e.g. riding within a channel. In this case, it will be necessary to provide some form of cable retention structure to ensure that the cable is retained in or adjacent to the arm sections (in sliding relation at least for the proximal telescopic sections). Protection for the cable might then be less than complete.

In a simple configuration, it will be noted that a single length of cable extending from proximal to the flange plate 7 to the rear guide mechanism 5 is sufficient free cable to allow for extension of a corresponding length of telescopic arm or arms. It is possible to allow for further extension of the telescopic arm by running the cable between the flange plate 7 and the rear guide mechanism 5 more than once in a pulley arrangement. In a general sense, the range of extension of the telescopic arm 11 will be approximately equal to the length of stored cable on the cable storage mechanism, and this in turn may be approximately equal to the length of the cable storage mechanism multiplied by the number of passes of cable from one end to another. Preferably, the individual passes of the cable along the cable storage mechanism are substantially parallel to one another.

In an alternative arrangement, a cable drum, about which the cable is wound, may be used to store the cable.

An advantage of the mechanism as shown in the figures is that the cable does not require a rotating coupling and less torsion is applied to the cable about its axis when compared with that which occurs with a cable drum.

Preferably, a bias mechanism is used to maintain the cable in tension such that when the telescopic arm is extended and retracted, all spare cable not used within the telescopic arm is safely stored on the cable storage mechanism 3. This could be provided by way of a spring bias on a cable drum to make the drum self-winding.

In use, an operator of the electronic surveillance device detector extends the telescopic arm against the cable tension bias to a desired length, where it is held by frictional resistance of the individual arm sections 1, 2 relative to one another or by some other suitable locking mechanism. The transducer head mounted at the distal end 13 of the telescopic arm 11 is thereby supported a desired distance from the base unit 15 at the proximal end 14 of the arm 11, and a counter-surveillance sweep may be performed.

The separation of the transducer head and the base unit may be varied at will and completely retracted upon completion. At all times, the cable 12 is substantially or completely protected from physical and/or mechanical damage by the arm sections 1, 2.

The overall length of cable 12 remains the same so that impedance matching of the cable to any signal processing circuitry can be controlled. In addition, in the preferred embodiment as shown in figure 1, the separation of the cable from other parts of the cable can be strictly controlled by the cable storage mechanism enabling control of capacitive or inductive effects that might otherwise interfere with transducer measurements.

Other embodiments are intentionally within the scope of the accompanying claims.

Claims (16)

1. A cable displacement mechanism for an electronic surveillance device detector comprising: a base unit housing a cable storage mechanism; a remote unit for housing at least one transducer for transmitting and/or receiving electromagnetic radiation; and a telescopic arm extending between the base unit and the remote unit, the telescopic arm having an electrical cable extending therethrough for electrically connecting the base unit and the remote unit.

2. The cable displacement mechanism of claim 1 in which the telescopic arm comprises a plurality of coaxial sections each at least partially retractable into the base unit.

3. The cable displacement mechanism of claim 1 in which the telescopic arm is hollow for passage of the electrical cable therethrough.

4. The cable displacement mechanism of claim 1 in which the cable storage mechanism is adapted to release cable into the telescopic arm as the telescopic arm is extended from a retracted position at least partially within the base unit.

5. The cable displacement mechanism of claim 4 in which the cable storage mechanism is adapted to receive cable from the telescopic arm as the telescopic arm is retracted, from an extended position, at least partially into the base unit.

6. The cable displacement mechanism of claim 4 or claim 5 in which the cable storage mechanism further includes a cable tensioning device for automatically releasing and retracting cable into and from the telescopic arm as the telescopic arm is extended or retracted by an operator thereof.

7. The cable displacement mechanism of claim 6 in which the cable tensioning device is adapted to maintain a substantially constant tension on the cable.

8. The cable displacement mechanism of claim 1 in which the cable storage mechanism comprises a support structure for supporting one or more lengths of the cable, which support structure extends and retracts within the base unit in concert with any extension and retraction of the telescopic arm to deliver cable into, and retract cable from, the telescopic arm.

9. The cable displacement mechanism of claim 8 in which the cable storage mechanism supports the cable parallel to the telescopic arm.

10. The cable displacement mechanism of claim 8 in which the range of extension of the support structure multiplied by the number of lengths of cable supported thereon is approximately equal to the overall range of extension of the telescopic arm.

11. The cable displacement mechanism of claim 10 in which multiple lengths of cable are supported on the support structure in substantially parallel disposition.

12. The cable displacement mechanism of claim 8 further including a control foil coupling two coaxial sections of the telescopic arm so that the sections extend out of and retract into the housing substantially simultaneously.

13. The cable displacement mechanism of claim 12 in which the control foil ensures that first and second coaxial section of the telescopic arm extend at substantially similar rates.

14. The cable displacement mechanism of claim 1 in which the remote unit is a transducer head.

15. A counter-surveillance electronic device detector comprising a cable displacement mechanism according to any preceding claim, in which the base unit further includes signal processing circuitry, and in which the remote unit houses at least one transducer for transmitting and/or receiving electromagnetic radiation, the electrical cable of the cable displacement mechanism electrically coupling the signal processing circuitry of the base unit to the at least one transducer in the remote unit, the telescopic arm structurally supporting the remote unit relative to the base unit.

16. A cable displacement mechanism substantially as described herein and with reference to the accompanying drawings.