BACKGROUND OF THE INVENTION Underwater machines or vessels for carrying out digging operations or other me- chanical operations are already known. In the off-shore oil industry it is known to use large and heavy manned or unmanned machines for digging and lifting operations and for mounting of valves. It is also known to use underwater digging machines for burying cables, which are constituted by ploughs drawn from the surface by a cable.

Bulldozers are also known which move on the sea-bed, being supplied and remotely controlled from the surface.

In US patent No. 3,990,377 is described a self-propelled machine for sea-bed work.

This machine comprises on the one hand a self-propelled chassis having an electri- cally powered hydraulic pumping system driven by a submersible motor fed through a cable connecting the chassis to the surface and, on the other hand, a submarine which fixes itself on a platform connected to the self-propelled chassis, and in which submarine the operators are installed. The submarine is fixed temporarily to the platform and induction coils enable orders to be transmitted between the submarine and the self-propelled chassis. The chassis disclosed in US patent No. 3,990,337 is moveable on the sea-bed by means of endless tracks and carries a plough for me- chanically burying an underwater cable unwound on the sea-bed. So, there is pro- vided a machine being effective in the specialised operation of burying an under- water cable.

It is seen that the machines of the prior art suffer from a common drawback in that they are constructed for special operations whereby the scope of application for these machines is limited.

It is also known to use small submarines in the form of Remote Operated Vessels, ROV, and Autonomous Underwater Vehicles, AUV, where a ROV is an unmanned submarine being remotely controlled from the surface and an AUV is an unmanned submarine being pre-programmed for a specific task. These submarines are mainly used for inspection jobs. It is further known to have small manned submarines being equipped with tools for performing mechanical tasks. A common drawback of these small submarines is that due to their small weight they are not capable of performing mechanical operations which involves a load above a few kilograms.

The above mentioned manned submarines may be divided in two types, a first type having an operator or pilot cabin with an internal pressure of 1 atmosphere corre- sponding to the surface pressure, whereby the pilots can raise directly to the surface without decompression. The second type is wet submarines or machines being controlled by swimming divers, which results in a limited depth and a limited time of diving due to a complex rising program in order to avoid diver's paralysis.

From the above discussion it may be understood that there is a need for an im- proved submarine system, which is flexible in operation and can be used for solving a number of underwater tasks including tasks involving heavy loads and tasks in- volving light loads.

Thus, it is an object of the present invention to provide such an improved submarine system, which system may be operated by unmanned submarines or manned sub- marines having a pilot at an internal pressure of about 1 atmosphere, and which system is flexible in operation and can be adapted for a number of different types of underwater tasks.

SUMMARY OF THE INVENTION In order to provide such an improved submarine system, the present invention pro- vides a submarine system comprising: a docking module having an upper part, and a submarine or an underwater vehicle with a lower part and with propeller means for moving the submarine or underwater vehicle through the water, said submarine or

underwater vehicle and said module comprising means for temporarily securing the submarine or underwater vehicle to the module.

According to an embodiment of the invention, the submarine or underwater vehicle may comprise means for collecting and/or storing data information. Preferably, the data may be stored in a digital form on a computer storage medium. When such data has been collected, there is a need for having means for getting access to the data or information without having the submarine or underwater vehicle passing to the surface. So, it is preferred that said submarine or underwater vehicle and said docking module comprise means for transmitting or communicating data information signals or control signals from the submarine or underwater vehicle to the docking module or from the module to the submarine or underwater vehicle. The docking module may further comprise means for storing information received from said data information signals or control signals. In order to further communicate the data in- formation or control signals, the docking module may be adapted for being con- nected to or communicating with an external data system. Thus, the data informa- tion signals or control signals may be transmitted from the submarine or underwater vehicle via the module to the external data system and/or external data information signals may be transmitted from the external data system via the module to the submarine or underwater vehicle.

The signal transmitting means may be based on different techniques. Thus, the transmitting means may comprise opto-electrical or electro-acoustic components, whereby the signals are transmitted between the submarine or underwater vehicle and the module as optical or acoustic signals. According to another embodiment of the invention the signal transmitting means may comprise a pair of signal induction coils, with one coil of said pair being arranged in the submarine or underwater vehi- cle and the other coil of said pair being arranged in the module.

When having a system with a submarine or underwater vehicle being temporarily secured to a docking module with signals being transmitted from the submarine to the module, it is important to have a well-defined interface of transmission between the submarine or underwater vehicle and the module. In order to establish such a well-defined interface, it is preferred that the upper part of the module has a trun- cated data guiding cone and the lower part of the submarine or underwater vehicle

has a truncated data guiding skirt. Here, opto-electrical or electro-acoustic transmit- ter components may be arranged adjacent a bottom surface of the data guiding skirt and opto-electrical or electro-acoustic receiver components may be arranged adja- cent a top surface of the data guiding cone. For embodiments in which the transmis- sion means comprises a pair of signal induction coils, one coil of the pair of signal induction coils may be arranged adjacent a bottom surface of the data guiding skirt and the other coil of the pair may be arranged adjacent a top surface of the corre- sponding data guiding cone.

It is preferred that the submarine or underwater vehicle of the present invention comprises one or more rechargeable batteries. In order to avoid that the submarine or underwater vehicle needs to go to the surface in order to recharge such batteries, it is therefore preferred that the docking module is adapted for being connected to a source of electric power, and that the submarine or underwater vehicle and the docking module comprise means for supplying electric energy from the power source via the docking module to the submarine or underwater vehicle. In order to establish such a well-defined interface of energy supply from the docking module to the submarine or underwater vehicle, it is preferred that the upper part of the dock- ing module has a truncated power guiding cone and the lower part of the submarine or underwater vehicle has a truncated power guiding skirt, where the electric energy supplying means are at least partly arranged in the power guiding cone and skirt.

In order to recharge the battery or batteries, the electric energy supplying means may be adapted for supplying electric energy to a battery within the submarine or underwater vehicle. Here, the electric energy supplying means may comprise a power transformer, with one half of the transformer having a primary coil wound around a core and being arranged in the docking module, and with the other half of the transformer having a secondary coil wound around a core and being arranged in the submarine or underwater vehicle. In an embodiment of the invention, the primary coil and the secondary coils are both wound around U-shaped cores, the two legs of each of said cores being oppositely arranged when the submarine or underwater vehicle is in place on the module. It is preferred that an air gap is provided between the two coils forming a pair of power coils, and it is also preferred that the electric energy supplying means comprises a switch mode power converter.

When the electric energy supplying means comprises a power transformer with a primary winding and a secondary winding, it is preferred that the core carrying the secondary winding is arranged adjacent a bottom surface of the power guiding skirt and the core carrying the primary winding is arranged adjacent a top surface of the corresponding power guiding cone.

When temporarily securing the submarine or underwater vehicle to the docking module, it is important that securing and release of the submarine or underwater vehicle can be done easily and fast. Thus, it is preferred that the means for tempo- rarily securing the submarine or underwater vehicle to the module comprises on or more securing electromagnets. Such securing electromagnets may be arranged in the submarine or underwater vehicle, or they may be arranged in the docking mod- ule. When the securing electromagnets are arranged in the module, the signal transmitting means may be adapted to transmit signals from the submarine or un- derwater vehicle to the module in order to control excitation of said securing elec- tromagnets, whereby a force of attraction is exerted on the submarine or underwater vehicle to hold the submarine or underwater vehicle temporarily fixed to the module.

It has already been mentioned that it is important to establish a well-defined inter- face between the submarine or underwater vehicle and the docking module in order to be able to transmit signals and exchange electric energy between the submarine or underwater vehicle and the docking module. One way of obtaining a well defined interface is to secure the submarine or underwater vehicle to the module at a well defined position. Thus, it is preferred that the docking module and the submarine or underwater vehicle comprise means for guiding and supporting the submarine or underwater vehicle in a well defined position on the module. Here, the upper part of the module may comprise at least three upward projecting truncated support guiding cones, and the lower part of the submarine or underwater vehicle may comprise at least three truncated support guiding skirts, each of said guiding cones being re- ceivable within a corresponding guiding skirt for guiding the submarine or underwa- ter vehicle in place on the module. Preferably, the support guiding cones are ar- ranged in a triangle with a corresponding triangle being formed by the support guid- ing skirts. The support guiding cones and skirts may have different dimensions, but it is preferred that the length or height of the side walls of the support guiding cones are larger than the length or height of the side walls of the corresponding support

guiding skirts, and the guiding skirts are formed so that when the submarine or un- derwater vehicle is on place on the module, the side walls of the guiding skirts rest on the side walls of the corresponding guiding cones.

For embodiments where securing electromagnets are arranged in the submarine or underwater vehicle, it is preferred that at least one of the securing electromagnets is arranged in the bottom of a guiding skirt. Preferably, each of the at least three guid- ing skirts has a securing electromagnet arranged in the bottom. According to an embodiment of the invention, a fixation spring is arranged adjacent to the bottom of a guiding skirt to hold the electromagnet at a distance from the top of the guiding cone when the electromagnet is not activated.

The docking module of the present invention may be used as a stand-alone module, but it may also be used in connection with a machine for carrying out operations on the sea-bed. Thus, the docking module may be adapted for being secured to a chassis or machine having means for carrying out mechanical operations on the sea-bed, said submarine or underwater vehicle, said module and said chassis com- prising means for transmitting control signals from the submarine or underwater ve- hicle via the module to the chassis in order to control said mechanical operations.

It is also within the scope of the invention to have the docking module as an integral part of such a machine. So, in this case the docking module according to the pres- ent invention may be a chassis or machine having means for carrying out mechani- cal operations on the sea-bed, said submarine or underwater vehicle and said chas- sis comprising means for transmitting control signals from the submarine or under- water vehicle to the chassis in order to control said mechanical operations.

When the submarine or underwater vehicle is controlling such a machine, the con- trol signals may be transmitted as data information signals by use of the signal transmitting means.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be further explained in the following with the aid of the accompa- nying drawing, in which

Fig. 1 illustrates an embodiment of a system of the present invention comprising a submarine and a docking module, Fig. 2 is a side view of an embodiment of a self-propelled chassis according to the present invention, Figs. 3a and 3b show a top-view and a side-view of an embodiment of a docking module of the present invention, Fig. 4 illustrates an embodiment of a support guiding cone and a support guiding skirt of the present invention in which a securing electromagnet is arranged in the guiding skirt, Fig. 5 illustrates an embodiment of a power guiding cone and a power guiding skirt of the present invention, and Fig. 6 illustrates an embodiment of a data guiding cone and a data guiding skirt of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS A submarine system according to the present invention comprises a self-propelled submarine or underwater vehicle and a docking module. Here it should be under- stood that the term submarine or underwater vehicle covers any form for manned or unmanned self-propelled underwater vehicle, including manned submarines where a pilot is operating the vehicle from a cabin having a normal surface pressure, manned wet submarines, and unmanned vehicles such as Remote Operated Ves- sels, ROV, and Autonomous Underwater Vehicles. In the following the term subma- rine will be used for any such underwater vehicle or vessel.

The submarine can be placed on the module from which position energy may be supplied to the submarine and data or control signals may be transmitted from the submarine to the docking station or from the docking station to the submarine.

Fig. 1 illustrates an embodiment of a system of the present invention comprising a submarine and a docking module.

The submarine 101 in Fig. 1 may be a submarine of a known type, for example an observation submarine comprising a body 102, which may contain one or two peo- ple for operating the submarine 101. The submarine 101 is self-propelled and com- prises means for moving the submarine 101 through the water. Such moving means may be one or more propellers, and the submarine may be equipped with side pro- pellers and/or vertical propellers, which propellers may be driven by electric motors.

The submarine 101 may comprise one or more rechargeable batteries and oxygen tanks or cylinders, which ensures an independent power to the propellers and an independent air supply. The submarine may also be equipped with side ballast.

The submarine 101 may also be equipped with a control panel inside the body 102, from which control panel an operator can control the submarine and forward data information or control signals to the docking module 201.

The docking module 201 may be arranged as a stand-alone module on the sea-bed, and the submarine 101 may dock the module 201 in order to get a supply of energy and/or in order to transmit information in the form of data signals. Here, the module 201 may be connected via a cable to an electric power source on the surface or to an electric power pack arranged on the sea-bed. The data information transmitted to the module 201 may be further transmitted to an external data or computer system.

Thus, the module 201 may be connected via a cable to an external data system on the surface or a data system arranged on the sea-bed. The module 201 may also or alternatively comprise data storage means for storing the information transmitted from the submarine 101. The stored data may then at a later stage be transferred to an external data or computer system.

Fig. 1 shows a particular embodiment of the invention in which the docking module 201 is fastened to the top of a chassis or machine 250 for mechanical handling operations. When the submarine 101 is in place on the module 102, the operator or operators of the submarine 101 can control the mechanical handling operations of tools connected to the chassis, by transmitting control signals via the module 201 to the chassis 250, whereby the mechanical operations and the movement of the

chassis may be controlled.

In Fig. 1 is further shown a transmission box 251 in the chassis 250 comprising means for controlling one or more electric motors 252 and/or one or more hydraulic motors 253 for driving the chassis 250, said controlling being based on signals transmitted from the submarine 101.

The module 201 and the submarine 101 may in preferred embodiments of the pres- ent invention comprise adaptations, which may consist in means for guiding and receiving the submarine, means for ensuring a temporary fixing of the submarine on the receiving means, means for transmitting data information or control signals be- tween the submarine and the module 201, and means for supplying the submarine with energy from the module 201. The module 201 may then have a plug serving as an electric power inlet for a cable from a power source, whereby the electric power may be supplied via the module 201 to the submarine 101. The module 201 may also or alternatively have a plug serving as a data transmission port or a control sig- nal port, whereby a data transmission cable or control signal cable may be con- nected to the module 201, whereby data or control signals may be transmitted from or to the submarine 101 via the module 201. The data transmission or control signal cable may be connected to the chassis 250 in order to transmit control signals from the submarine 101 to the chassis 250. If the module 201 is operating as a docking module, the data transmission or control signal cable may be connected to an exter- nal computer or data system, whereby data or control signals may be transmitted between the submarine 101 and the external data system via the module 201.

Fig. 1 further illustrates an embodiment of the invention in which three support guiding cones 203,204,205 are arranged on the upper surface or part of the mod- ule 201 with corresponding hollowings formed as support guiding skirts 103,104, 105 being arranged in the lower part of the submarine 101. Fig. 1 also illustrates an embodiment of the invention in which a power guiding cone 206 and a data guiding cone 207 are arranged on the upper part of the module 201 with a corresponding power guiding skirt 106 and a corresponding data guiding skirt 107 being arranged in the lower part of the submarine 101. It is preferred that the upper part or surface of the module 201 forms a substantially planar surface on which the cones are ar- ranged. The support guiding cones 203,204,205 are preferred to be truncated

cones having an upper surface substantially in the same plane. The power and data cones are also preferred to be truncated cones having an upper surface substan- tially in the same plane. According to the embodiment of Fig. 1. the height of the data and power cones 207,206 may be smaller than the height of the guiding cones 203,204,205.

It is preferred that the depth of the support guiding skirts 103,104,105 is shorter than the height of the support guiding cones 203,204,205, whereby the submarine 101 may be resting on the truncated guiding cones 203,204,205 when being guided in place on the module 201. The guiding means 103,104,105 and 203,204, 204 are preferably arranged so as to form a triangle. Thus, when the submarine 101 is resting on the three truncated cones 203,204,205 arranged in a triangle as illus- trated by Fig. 1, a very stable positioning of the submarine 101 on the module 201 is obtained.

The chassis 250 of Fig. 1 may have a frame 255 with an upper part formed as a platform on which the module 201 may be steadily secured or fastened to the chas- sis 250. In an alternative embodiment according to the invention, the module 201 is an integral part of the chassis 250, whereby the chassis 250 itself operates as a docking module. In this embodiment the control signals are transmitted directly be- tween the submarine 101 and the chassis 250.

The chassis 250 may correspond to the chassis of a self-propelled machine used on the surface, and it may have moving means in the form of two endless tracks 260a, 260b driven by hydraulic motors supplied by an electrically powered hydraulic pumping system. The electric motor driving the hydraulic system may be a sub- mersible motor supplied through an electric cable. The cable may be powered from the surface or may alternatively be powered from a power pack arranged on the sea-bed. Several sets of tools may be connected to the chassis 250 in order to per- form different mechanical operations.

In Fig. 2 is shown an embodiment of a chassis 250, where the different guiding cones 203,204,205 and/or 206,207 are an integral part of the chassis 250. Here, a digging arm 261 carrying a shovel 262 may be mounted on the chassis 250, whereby the chassis 250 is equipped for performing digging operations on the sea-bed, and a

bulldozer shovel 263 may also be mounted on the chassis 250. In Fig. 2 is also shown other types of tools, which may be connected to the chassis 250 such as a hydraulic hammer 264, a drilling machine 265 and a suction pipe 266 for suction of sand. One or more hydraulic power terminals 267 may be arranged on the chassis 250 in order to provide hydraulic power to the hydraulic tools.

In Figs. 3a and 3b are shown a top-view and a side-view, respectively of an em- bodiment of a docking module according to the present invention. The module of Figs. 3a and 3b is similar to the docking module of Fig. 1 and the reference numbers used for the module of Fig. 1 are also used in Figs. 3a and 3b. Thus, the illustrated module 201 has three truncated support guiding cones 204,205,206 and a trun- cated power guiding cone 206 and a truncated data guiding cone 207. The module 201 is preferably built as a frame of stainless steel with the guiding cones 203,204, 205 arranged to form a triangle. It is preferred that the height and the diameter of the power and data cones 206,207 are smaller than the height and the diameter of the guiding cones 203,204,205.

The embodiment of the docking module 201 illustrated in Fig. 3 comprises three support guiding cones 203,204,205 for guiding the submarine 101 in place and for supporting the submarine 101. However, it is also within the invention to use more than three guiding and supporting cones, such as for example 4,5 or 6 cones.

According to the present invention the submarine 101 and the docking module 201 comprise securing means for temporarily securing the submarine 101 to the module 201. It is preferred to use electromagnets for securing the submarine 101 to the module 201. An arrangement of such an electromagnet is illustrated in Fig. 4, which shows an embodiment of a support guiding cone 203 of the module 101 and a sup- port guiding skirt 103 of the submarine in which a securing electromagnet 410 is arranged in the guiding skirt 103.

The guiding skirt 103 in Fig. 4 has a lowered bottom 411 holding the electromagnet 410. A fixation spring 412 is provided adjacent the inside of the bottom 411 being hold in position by a fixation bolt 413. Electric power (not shown) is delivered by the submarine 101 to the electromagnet 410 in order to activate the electromagnet 410 when the submarine 101 has been guided in place on the module 201. Fig. 4a illus-

trates the situation when the submarine 101 is not yet fully in place on the module 201 and the electromagnet 410 is not activated. When the submarine 101 is in place on the module and the electromagnet 410 is not activated, the electromagnet 410 will not be in contact with the guiding cone 203, whereas the side walls of the guid- ing skirt 103 will be resting on the side walls of the guiding cone 203. Fig. 4b illus- trates the situation when the submarine 101 is in place on the module 201 and the electromagnet 411 has been activated. Here, the fixation spring 412 is in a com- pressed position and the electromagnet 411 is in magnetic contact with the top of the cone 103, whereby the submarine 101 is temporarily secured to the module 201.

According to an embodiment of the invention, a securing electromagnet may be ar- ranged in all the support guiding skirts, but in case the submarine has more than three support guiding skirts, it is also within the scope of the invention to have only part of the skirts comprising a securing electromagnet. However, it is preferred that at least three securing electromagnets are provided.

In order to obtain a good magnetic contact between the electromagnet 411 and the cone 203, the top of the cone may be made from a material such as mild steel.

Fig. 5 illustrates an embodiment of the present invention in which means 51 Oa, 51 Ob for supplying electrical energy from the module 201 to the submarine 101 is ar- ranged in a power guiding cone 506a of the module 210 and a power guiding skirt 506b of the submarine. Here the energy supplying means 510a, 510b comprises a pair of power induction coils wound around cores, whereby a power transformer is provided with the primary winding of the transformer 510a being arranged in the cone 506a and the secondary winding of the transformer 51 Ob being arranged in the, skirt 506b. In an embodiment of the invention an external DC-voltage source (not shown) supplies a DC-voltage via a power plug 511 in the module 201 and a power cable 512 to a DC/AC converter (not shown) arranged in the module 201, from where an AC-voltage is delivered to the primary coil 510a in the cone 506a. An AC- signal is received by the secondary coil 510b in the skirt 506b, from where the signal is fed via a cable 515 to an AC/DC converter arranged in the submarine. The AC/DC converter delivers a DC-voltage, whereby a rechargeable battery arranged in the submarine 101 is being recharged. So, the batteries of the submarine 101 is being

recharged while the submarine is resting on the module 201, with the result that the submarine does not have to pass to the surface in order to be recharged.

In a preferred embodiment, both cores of the transformer 510a, 510b are formed in a U-shape. The two legs of the primary core in the cone 506a are opposed to the two legs of the secondary core in the skirt 506b when the submarine 101 is in posi- tion on the module 201. It is preferred that an air-gap of a few millimetres exists between the two oppositely arranged cores, whereby a switch-mode power con- verter or transformer may be provided, resulting in a relatively high power conver- sion efficiency.

According to the embodiment of the invention illustrated in Fig. 5, the power guiding cone 506a is steadily fixed to the upper part of the docking module 101, whereas the power guiding skirt 506b is movable connected to the lower part of the submarine 101. The skirt 506b may be connected to the submarine 101 by 4 fixation bolts 513 having compression springs 514, and the lower part of the power skirt 506b may be formed so as to a fit to the upper part of the power cone 506a. Thus, when the sub- marine 101 is guided in place on the module 201, the compression springs 514 al- lows a movement of the power skirt 506b in the vertical direction and also a slight movement in the horizontal direction, whereby the power skirt 506b may be brought in contact with the power cone at a wanted or predetermined position.

Fig. 6 illustrates an embodiment of a data guiding cone 607a and a data guiding skirt 607b of the present invention. It is preferred that the mechanical formation of the data cone 607a and the data skirt 607b is almost identical to the formation of the power cone and skirt, 506a and 506b. Thus, the data guiding cone 607a is steadily fixed to the upper part of the docking module 101, whereas the data guiding skirt 607b is movable connected to the lower part of the submarine 101. The skirt 607b may be connected to the submarine 101 by 4 fixation bolts 613 having com- pression springs 614, and the lower part of the data skirt 607b may be formed so as to a fit to the upper part of the data cone 607a.

In the embodiment of the invention shown in Fig. 6, means for directing data infor- mation signals or controls signals from the submarine 101 to the docking module 101 comprises data or signal transmission means 610b arranged in the data skirt

607b and corresponding data or control signal receiving means 610a arranged in the data cone 607a. The transmission means 610b is arranged in the bottom of the skirt 607b with the receiving means 610a being arranged at the top of the cone 607a. The signal to be transmitted from the submarine 101 is forwarded to the transmission means 610b via a cable 615, and the signal received by the receiving means 610a is forwarded via a cable 612 to a data plug 611, from where further connections can be made to an external data or computer system, or from where connections can be made to a machine when signals are to be forwarded from the submarine to a machine.

In a particular embodiment of the invention the data or control signal transmission and receiving means, 610b and 610a, are opto-electrical components, whereby sig- nals are communicated between the submarine 101 and the docking module 201 as optical signals. For the opto-electrical components of the transmitting and receiving means, 61 Ob and 61 osa, the transmitter components 61 Ob may comprise a converter for converting an electrical signal to an optical signal, and the receiver components 610a may comprise a converter for converting an optical signal to an electrical sig- nal. Hence, the signals may be forwarded to the data skirt 607b as electric signals, and the signals may be forwarded from the data cone 607a to the data plug 611 a electric signals. However, the signals may also be forwarded to the data skirt 607a as optical signals, and from the data cone 607a to the plug 611 as optical signals.

In another embodiment of the invention, the data or control signal transmission and receiving means, 610b and 610a, may be electro-acoustic components, where sig- nals are communicated between the submarine 101 and the docking module 201 as acoustic signals.

In still another embodiment of the invention, the data or control signal transmission and receiving means, 610b and 610a, may comprise one or more pair of induction coils. Here, a pair of induction coils may be placed opposite each other, one at the bottom of the skirt 607b and the other at the top of the cone 607a. Due to the forma- tion of the skirt 607b and the cone 607a, only a relatively small air-gap in the range of a few millimetres may exist between the coils when the submarine 101 is in posi- tion, whereby a relatively good coupling between the coils may be obtained.

It should be understood that electrical circuits or transmitter means of the submarine 101 may be powered by a rechargeable battery mounted in the submarine 101.

Similarly, electrical circuits or receiving means of the docking module 201 may be powered by a rechargeable battery mounted in the module 201. However, electrical power may also be supplied directly to the docking module 201, whereby a battery may not be needed in the module 201.

It should be understood that the foregoing description of the invention is intended to merely be illustrative thereof and that other embodiments and modifications may be apparent to those skilled in the art without departing from the spirit and within the scope of the appended claims.