GB2393326A

GB2393326A - Shielding electronic devices from electromagnetic radiation

Info

Publication number: GB2393326A
Application number: GB0221990A
Authority: GB
Inventors: Arthur Cheumin Woo
Original assignee: Hewlett Packard Co
Current assignee: HP Inc
Priority date: 2002-09-21
Filing date: 2002-09-21
Publication date: 2004-03-24
Also published as: GB0221990D0

Abstract

A signal processor, e.g. a pre-amplifier 410a, 410b, is at least partially housed within a recess 415 in an electrically conductive chassis 407 and thereby screened from electromagnetic radiation. A printed circuit board (PCB) 408 covers the recess and is in electrical contact with the chassis 407 via the ground plane 417 and is connected to the controller 414 via the solid connector 412. The signal processors may receive an input from a data transfer head 404. In an alternative embodiment (Fig 5) the PCB and controller are both on the same side of the chassis. An arrangement is also described (Fig 6) in which a processor such as a pre-amp is mounted on a conductive chassis and has a conductive cover (604) in contact with the chassis.

Description

ELECTRONIC DEVICE, DATA STORAGE DEVICE, DATA

READING DEVICE, METHOD OF MANUFACTURE OF AN

ELECTRONIC DEVICE, METHOD OF REDUCING INDUCTANCE

OF A SIGNAL CARRIER IN A DATA READING DEVICE AND

5 METHOD OF SCREENING A SIGNAL PROCESSOR IN AN

ELECTRONIC DEVICE

This invention relates to an electronic device, a data storage device, a data reading device, a method of manufacture of an electronic device, a 10 method of reducing inductance of a signal carrier in a data reading device and a method of screening a signal processor in an electronic device.

Low power signals within a device, for example from a read head of a tape drive, are prone to contamination due to electromagnetic (e/m) 15 radiation. The e/m radiation typically originates from other circuitry associated with the device. This problem is of particular importance in a data transfer device such as a tape drive where low power signals originating from the read head typically pass to a pre-amplifier (pre-amp) before having the data decoded. Corruption of the low power signal 20 results in corruption of the data. Noise due to e/m radiation from drive circuitry and controller circuitry is a major source of corruption of data.

In order to reduce this contamination the pre-amplifiers are at present commonly mounted upon a separate printed circuit board to the drive circuitry and the controller circuitry.

Another problem associated with tape drives is that in the prior art a long

flexible connector is used to connect the read head to the pre-amp, the pre-amp typically being mounted on the opposite side of a chassis of the drive from the read head. This long flexible connector not only provides 30 a significant opportunity for e/m contamination of low power signals to occur but also slows signals due to a large inductance associated with the

connector. This may limit the maximum data transfer rate achievable using this arrangement, and may have other associated problems.

The use of a chassis of a computer to prevent e/m contamination and 5 radio-frequency (rf) contamination escaping the body of a computer is known, see for example US 6,023,415. This does however require the use of special gaskets in order to effectively seal input and output ports to prevent the egress of e/m and rf radiation out of the computer chassis.

10 The use of a specially designed shielding housing to screen a printed circuit boards (PCB) from e/m and rf radiation is also known, see for example US 6,137,051. These housings increase the size of the PCB unit and therefore increase the overall size of any device manufactured including them. They also increase the cost of manufacture of the PCB 15 and device as additional components must be manufactured.

According to a first aspect of the present invention there is provided an electronic device comprising an electrically conductive chassis and a signal processor, said chassis having a recess in a portion thereof, said 20 recess being defined at least in part by at least one electrically conductive surface of said chassis, and wherein said processor is located in said recess such that said at least one electrically conductive inner surface is arranged to at least partially shield said processor from electromagnetic radiation. This arrangement allows a signal processor, for example a pre-amplifier associated with a read head of a tape drive, to be screened from e/m radiation, in some embodiments without requiring the manufacture of additional parts.

The chassis may have a generally planar face surface and said recess may be provided in said face surface. Said signal processor may be wholly, or substantially wholly, received in said recess so as to have no or little projection above said face surface.

The recess may be provided with a conducting cover, such as a plate, a mesh or a grid, which may be in electrical contact with the chassis. This improves the efficiency of the e/m screening by effectively providing a Faraday cage in which the processor is held. The cover may form part of 10 a printed circuit board (PCB), for example a ground plane, to which the processor may be connected. Alternatively the cover may be a metal sheet, which, possibly, is flexible.

The signal processor may have an input arranged to receive a signal from 15 a circuit element and an output arranged to transmit a processed signal to a circuit. The signal processor may be a pre-amplifier (pre-amp) . The circuit may be a controller circuit. The circuit element and the recess may be disposed on one side of the chassis.

20 The signal processor may be at least partially within the thickness of a wall defining said recess. Preferably, the signal processor is substantially wholly within the thickness of said wall.

The chassis may have a plate, which may define the recess. The plate may 25 be a base plate upon which are mounted components of the device. The plate is preferably a structural plate which may give significant structural strength to said chassis. The chassis preferably has said base plate extending transversely between first and second opposed chassis walls.

30 The recess in the base plate may have a chip therein, typically a pre-

amplifier. The recess may have a depth of about ah - 3h (preferably

about i/) of the thickness of the base plate, and base plate may have a thickness of 2mm or more, preferably 2-lOmm, most preferably about 3mm or 4mm + lmm.

5 It will be appreciated that the term signal processor as used herein encompasses both analogue signal processing devices such as pre-

amplifiers and also digital signal processors.

It will be further appreciated that the electrically conductive surface of 10 the recess can also act to, at least partially, constrain electromagnetic radiation within the recess and, at least partially, screen external circuitry from a radiation source located within the recess.

According to a second aspect of the present invention there is provided a 15 data reading device comprising a data read head for reading data from a data storage medium, an electrically conductive chassis arranged to at least partially enclose said data storage medium and having first and second signal processors attached thereto, a first connector for connecting said read head to said first signal processor, and a second connector for 20 connecting said first and second signal processors; wherein at least one of said connectors passes through said chassis.

This arrangement contrasts with the prior art arrangements wherein the

connection between the first and second processors is made by passing 25 around the chassis rather than passing through it. Passing through the chassis allows the distance between the read head and the processor to be reduced by providing a direct path. The reduction of said distance reduces the opportunity for e/m contamination of the read signal, and decreases the inductance of the arrangement thereby increasing the speed of signal 30 transfer that is possible between the read head and the first signal processor.

Preferably an opening is provided in said chassis to allow said connector to pass therethrough.

5 The first signal processor may be a pre-amplifier (pre-amp) that is typically arranged to amplify a signal from the read head. The first signal processor, typically a pre-amp, may be located within the chassis.

This minimises the distance that a signal from the read head must travel before being amplified, thus decreasing the opportunity for e/m 10 contamination of the signal increasing signal to noise ratio at the pre-

amplifier and therefore data integrity.

There may be provided a heat conductive pad arranged to contact both the chassis and the first signal processor simultaneously. Thus, heat from the 15 signal processor can be efficiently transferred to the chassis which then acts as a heat sink.

The chassis may have a recess therein, in which the first signal processor may be located. The recess may have a conductive cover that may be in 20 electrical contact with the chassis. The cover may be a ground plane of a PCB to which the first processor may be connected. The first connector may be arranged to pass through an opening in the cover. The second connector may be arranged to pass through an opening in the chassis.

The recess may be located in a face of the chassis adjacent the data read 25 head.

Having the flexible connector extend through the chassis allows a pre-amp to be located nearer to the read head than is achieved in the prior art.

Thus, e/m contamination and inductance of a signal path are typically 30 reduced, resulting in better signal to noise ratios at the pre-amp and higher data transfer rates being achievable.

The use of a Faraday cage type arrangement to screen the pre-amp further reduces e/m contamination as the pre-amps are effectively screened from both the drive circuitry and the controller circuitry. Providing the 5 Faraday cage within the thickness of a base plate is convenient and simple, and takes up no extra room.

The read head may be moveable relative to the housing. The first connector may be a flexible connector, for example a flexible flat 10 connector and maybe a ribbon cable, or the like. The relative motion of the read head with respect to the housing makes the use of a flexible connector desirable.

It will be appreciated that the present invention is not limited to for 15 example, tape drives but may be applied to any device having a read head connected to a first signal processor, for example a disc drive, or indeed any similar device.

According to a third aspect of the present invention there is provided a 20 screening arrangement for a signal processor comprising an electrically conductive chassis having a recess and a signal processor received in said recess, and an electrically conductive cover, and said cover and said chassis being in electrical contact, and said processor being substantially enclosed in said recess by said chassis and said cover in combination.

This arrangement provides for a substantially electric field free zone

within the chassis and cover, thereby screening the processor from external electric fields and reducing e/m contamination of signals therein.

30 The processor may be in a recess in the chassis. The processor may be mounted on a surface of the chassis. Alternatively, the processor may be

mounted upon a surface of the cover. In a further alternative the processor may be mounted on a printed circuit board disposed next to, or attached to, either, or both, of the chassis and cover.

5 The processor may form part of a tape drive. The processor may be arranged to receive signals from a read head of a device, for example a tape drive.

According to a fourth aspect of the present invention there is provided an 10 electronic device comprising electrically conductive chassis means for supporting components of the electronic device, signal processing means for processing signals, said chassis means having a recess therein, said processing means being located in said recess, such that, in use, at least one electrically conductive wall of said recess is arranged to at least 15 partially screen said processing means from electromagnetic radiation.

According to a fifth aspect of the present invention there is provided a data reading device comprising data reading means for reading data from a data storage medium, chassis means for supporting components of said 20 data reading device, first signal processing means for processing signals, first connecting means for connecting said data reading means to said first signal processing means, second signal processing means for processing signals, second connection means for connecting said first and second signal processing means; wherein at least one of said connection means 25 passes through said chassis means.

Preferably said first connecting means passes through said chassis means.

Preferably said first processing means is disposed between said chassis means and said second processing means. Preferably said first processing 30 means comprises a pre-amplifier and said second processing means comprises a signal processor. The chassis means may be a plate, and the

pre-amplifier may be closer to the plate than is the signal processor (i. e. the signal processor may be disposed laterally further away from the plate). This may reduce the signal path between the data reading means and the pre-amp. The pre-amp may be the same side of the plate as the 5 data reading means, and the signal processor on the other side of the plate, with the second connecting means extending through the plate.

According to a sixth aspect of the present invention there is provided a screening arrangement for one or more signal processing means 10 comprising electrically conductive chassis means for supporting one or more components, and electrically conductive cover means, said cover means and said chassis means being in electrical contact, said processing means being substantially enclosed by said chassis means and said cover means. According to a seventh aspect of the present invention there is provided a data reading device comprising a data read head for reading data from a data storage medium, an electrically conductive chassis arranged to at least partially enclose said data storage medium; a first signal processor; 20 a first connector for connecting said read head to said first signal processor; a second signal processor; a second connector for connecting said first and second signal processors; an electrically conductive cover, and wherein said chassis defines a recess adjacent said read head and said first signal processor is located in said recess in said chassis, said 25 electrically conductive cover extending over said first signal processor and being in electrical contact with said chassis so as to substantially enclose said first processor, and wherein said second connector passes through said chassis.

30 According to an eighth aspect of the present invention there is provided a method of manufacturing an electronic device comprising the steps of:

i) attaching a circuit element to a conductive chassis plate; and ii) connecting the circuit element to a signal processor via a passageway through said chassis plate.

5 The method may include keying the passageway. This prevents misalignment of the circuit element relative to the processor.

The method may include providing the circuit element in the form of a read head of the device. Alternatively, the method may include providing 10 the circuit element in the form of a pre-amp or a circuit board having a pre-amp mounted thereupon.

According to a ninth aspect of the present invention there is provided a method of reducing inductance of a signal carrier in a data reading device 15 comprising: i) connecting a signal carrier to a read head; and ii) connecting said read head to a signal processor via a passageway through a chassis plate.

20 According to a tenth aspect of the present invention there is provided a method of screening a signal processor of an electronic device comprising the steps of: i) providing a recess in an electrically conducting chassis of said device; and 25 ii) placing the processor in said recess.

Preferably the method comprises: iii) at least partially covering an opening of said recess with an electrically conducting cover; and 30 iv) electrically contacting said cover to said chassis.

According to an eleventh aspect of the present invention there is provided a signal processing apparatus comprising a read head arranged to read data from a data storage medium, first and second transmission elements, and a signal processor; said first transmission element connecting said 5 read head to said signal processor, and said read head being arranged to generate a signal indicative of data upon said data storage medium, said first transmission element being arranged to carry said signal from said read head to said processor, and said second transmission element being arranged to carry a processed signal from said processor; and wherein 10 said read head is mounted on a chassis plate to a first side of said plate and said plate has an aperture, said second transmission element extending through said aperture to a second side of said plate.

The first transmission element may be a flexible connector. The second 15 transmission element may be a rigid connector.

According to another aspect the invention comprises screening a processor of an electronic device from electromagnetic interference by housing said processor in a recess defined in a metal support plate, which 20 support plate also mounts other electrical components of said device.

Preferably the processor is enclosed in said recess by covering said recess with an electrically conductive cover.

25 The invention will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 is a schematic representation of a tape data reader of the prior art;

Figure la is a schematic view of the tape data reader of Figure 1; Figure 2 is a schematic view of a housing of a tape data reader of 5 the prior art;

Figure 3 is a schematic sectional view of a tape data reader according to the prior art;

10 Figure 4 is a schematic sectional view of a first embodiment of a tape data reader incorporating at least an aspect of the present invention; Figure 5 is a schematic sectional view of a second embodiment of 15 a tape data reader incorporating at least an aspect of the present invention; Figure 6 is a schematic representation of a screening arrangement according to an aspect of the present invention; and Figure 7 is a schematic representation of a signal processing apparatus according to an aspect of the present invention.

Referring now to Figures 1 and la, a tape data reader 100 comprises a 25 chassis plate 102 upon which are mounted tape guides 104a,b, drive spools 106a,b and an activation arm 108. The arm 108 has a read head 110 attached at an end thereof. A flexible connector 112 connects the read head 110 to a pre-amp circuit board 113 (shown in dotted outline) that is mounted on an opposite side of the chassis plate 102 to the head 30 110. The connector 110 passes over an edge of the plate 102 in order to connect to the pre-amp circuit board 113.

A cassette 114 containing a data storage tape 115 is inserted into the tape data reader 100 such that the tape guides 104a,b guide the tape 115 over drive spools 106a,b. The activation arm 108 moves the read head 110 5 into contact with the tape 115. A voltage signal generated at the read head 110 in response to the contents of the tape 115 and this signal passes via this flexible connector 112 to the pre-amp circuit board.

Referring now to Figure 2, a housing 200 of the data reader 100 10 comprises an H-shaped chassis 202 and a casing 204. The chassis 202 comprises two side walls 206a,b and a chassis plate 208 (corresponding to the chassis plate 102 of Figure 1). The flexible connector 112, of Figure 1, passes over one of the side walls for example 206a between the chassis 202 and the casing 204 in order to connect the read head 110 to the pre 15 amp circuit board that is mounted on an opposite face of the chassis plate 208 to the read head 110. The chassis plate 208 is typically a heavy gauge plate, usually 5-lOmm thick, with stiffening ribs in order to support the data reader 100.

20 Referring now to Figure 3, a tape reader 300 of the prior art comprises an

actuator 302, a read head 304, a flexible connector 306, a metal H-shaped chassis 307, a pre-amp printed circuit board (PCB) 308, two pre-amps 310a, b, a connector 312 and a main controller PCB 314.

25 The actuator 302 is mounted upon one surface of a chassis plate 315. The read head 304 is mounted to one side of the actuator 302 and has the flexible connector 306 connected thereto. A rolling loop, the part of the flexible connector which is arcuate and connects a moving part to a fixed point, of the flexible connector 306 passes over a side wall 316 of the 30 chassis 307 and is connected to the pre-amp PCB 308 mounted upon an opposite surface of the chassis plate 315 to the actuator 302. The pre

amp PCB 308 has the pre-amps 310a,b mounted thereupon, typically the preamps 310a,b are application specific integrated circuits (ASICs), and is connected to the controller PCB 314 by the solid connector 312.

5 In use, the actuator 302 moves the read head 304 into contact with tape 316 that is spooling past the head 304.

The interaction of aligned magnetic domains in the tape 318 with the head 304 generates a small signal voltage at the read head 304 typically 10 200-300mV. The signal voltage passes down the flexible connector 306 to the pre-amp PCB 308 where the signal voltage is amplified in the pre amplifiers 310a,b. The amplified voltage passes from to pre-amp PCB 308 to the controller PCB 314 via the solid connector 312 where subsequent processing of the signal takes place.

This arrangement suffers from the problem that the length of flexible connection 306 extending between the read head 304 and the pre-amp PCB 308 is large, typically 12 cm long. Therefore, there is a high risk of contamination of the small signal voltage by electromagnetic (e/m) 20 radiation originating from, for example the actuator 302, the controller PCB 314 or drive circuitry of tape spools. Also the pre-amps 310a,b are exposed and are therefore subject to e/m contamination of signals thereupon. 25 Additionally, the large lengths of the flexible connector 306 results in a high impedance to the signal voltage that will slow signals down and limit data transfer rates of the tape reader 300.

Referring now to Figure 4, a tape reader 400 comprises an actuator 402, 30 a read head 404, a flexible connector 406, a metal chassis 407, a pre- amp

PCB 408 having two pre-amps 410a,b mounted thereupon, two thermal contacts 411a,b, a solid connector 412 and a main controller PCB 414.

The chassis 407 has a recess 415 in one surface thereof. The pre-amp 5 PCB 408 is placed over the recess such that the pre-amps 410a,b are located in a substantially enclosed chamber 416. A ground plane 417 of the PCB 408 is in electrical contact with the metallic chassis 407. The actuator 402 is located on the pre-amp PCB 408 remote from the chassis 407 and the read head 404 projects from a side of the actuator 402.

The thermal contacts 411a,b are located between the pre-amps 410a,b and a surface 418 of the recess such that there is a thermally conductive path between the pre-amps 410a, b and the chassis 407.

15 A passageway 420 passes through the chassis 407, the chassis typically being 2-3mm thick opening into the recess 415, which is typically 1-2mm deep i.e. approximately half the thickness of the recess through the surface 418. The solid connector 412 passes through the passageway 420 connecting the pre-amp PCB 408 and the controller PCB 414 and is 20 insulated from the chassis 407. The passageway 420 is typically keyed so as to prevent incorrect relative orientations of the pre-amp PCB 408, connector 412 and controller PCB 414. The keying of the passageway 420 improves the assembility of the actuator 402 and the associated electronics into the tape reader 400.

The actuator 402 moves the read head 404 into contact with tape 422. A signal voltage is generated, as described hereinbefore and passes down the flexible connector 406 to the pre-amp PCB 408 where the signals are amplified at the pre-amps 410a,b. The amplified signals then pass along 30 the solid connector 412 to the controller PCB 414 for further processing.

The electrical contact between the ground plane 417 and the chassis 407 effectively creates a Faraday cage around the pre-amps 410a,b that reduces e/m radiation contamination of the low voltage signals is the PCB 408 and the pre-amps 410a,b.

Additionally, by contacting the flexible connector 406 directly to the pre amp PCB 408 (instead of going around the side walls of the chassis) the length of the connector 406 is reduced. This reduces the opportunities for e/m interference with the small signal voltage carried by the connector 10 406 and also reduces the inductance of the signal path thereby allowing increased data transfer rates over the prior art arrangements.

The thermal contacts 411a,b allow heat generated by the pre-amps 410a,b to be distributed into the chassis 407. This contrasts with the prior art

15 where the heat went into heat sink pads on a PCB.

It will be appreciated that the thermal contacts 412a,b need not be provided and that the pre-amps 410a,b may contact the surface 418 directly. Referring now to Figure 5, a second embodiment of a tape reader 500, incorporating at least one aspect of the present invention, comprises an actuator 502, a read head 504, a flexible connector 506, a metal chassis 507, a pre-amp PCB 508 having two pre-amps 51 Oa, b mounted 25 thereupon, a solid connector 512 and a main controller PCB 514. The connector 506 passes through a passageway 515 through the chassis 507 to connect with the pre-amp PCB 508.

The chassis 507 has a recess 516 therein which is closed by the pre-amp 30 PCB 508, such that the pre-amps 510a,b are received into the recess 516.

A ground plane 517 of the pre-amp PCB 518 is in electrical contact with the chassis 507.

This arrangement reduces the length of the flexible connector compared to 5 the prior art, by passing through the chassis 507 and the pre-amps 510a, b

are retained in the Faraday cage like recess 516 that reduces the effect of e/m interference with signals in the pre-amps 510a,b.

Referring now to Figure 6, a processor 600, for example a pre-amp, is 10 mounted upon an electrically conductive chassis 602 and has an electrically conductive cover 604 thereover that is in contact with the chassis 602. Thus, the processor 600 is within a Faraday cage like arrangement of the chassis 602 and cover 604.

15 An input signal 605 passes into the processor 600 and an output signal 606 passes out of the processor 600 along connectors, for example wires, tracks or flexible connectors through openings in the cover 604.

It will be appreciated that the connectors may pass through openings in 20 the chassis 602, or the cover 604.

Referring now to Figure 7 a signal processing apparatus 700 comprises a read head 702, a flexible connector 704, a pre-amplifier 706 and a rigid connector 708.

The flexible connector 704 connects the read head 702 to the pre-

amplifier 706, The read head 702 reads data from a data storage medium and a signal indicative of the data is passed from the read head 702 to the pre-amplifier 706 via the flexible connector 704.The pre-amplifier 706 30 amplifies the signal and the amplified signal is output via the rigid connector 708.

The rigid connector 708 passes through the chassis 710 to further signal processing circuitry 712. The signal is now not as prone to the effects of electromagnetic contamination as prior to pre-amplification as the 5 increased signal strength following pre-amplification gives a better signal to noise ration for a given strength of contaminant electromagnetic field.

Thus, signal integrity is increased over prior art arrangements.

It will be further appreciated that although described with reference to 10 tape readers the present invention is applicable to any electrical device where screening of a signal processor is desirable and a chassis is available upon which to mount the processor, for example, a CD reader, a DVD reader, a magnetic disc reader or a magnetic-optical disc reader.

15 It will be still further appreciated that the arrangements described herein do not relate to test equipment suitable for testing pre-amplifier, or other signal processing circuitry, but relate to commercial systems where high signal to noise ratios are desirable. That is to say, the devices are commercial items suitable for sale as they stand to performtheir purpose 20 (e.g. they may be a tape drive, disc drive, or the like).

Claims

1. An electronic device comprising an electrically conductive chassis and a signal processor, said chassis having a recess in a portion thereof, 5 said recess being defined at least in part by at least one electrically conductive surface of said chassis, and wherein said processor is located in said recess such that at least one electrically conductive inner surface is arranged to at least partially shield said processor from electromagnetic radiation. 2. A device according to claim 1 wherein the recess is provided with a conducting cover that is in electrical contact with said chassis, wherein said cover is selected from the following list: a plate, a mesh, a grid.

15 3. A device according to claim 2 wherein said cover is a ground plane of a printed circuit board upon which said processor is mounted.

4. A device according to any preceding claim wherein said signal processor has an input arranged to receive a signal from a data transfer 20 head.

5. A device according to claim 4 wherein said data transfer head and said recess are disposed to one side of said chassis.

25 6. A device according to any preceding claim wherein said signal processor is a pre-amplifier.

7. A device according to any preceding claim wherein said chassis has a plate which defines said recess.

8. A data reading device comprising a data read head for reading data from a data storage medium, an electrically conductive chassis arranged to at least partially enclose said data storage medium and having first and second signal processors attached thereto, a first connector for connecting 5 said read head to said first signal processor, and a second connector for connecting said first and second signal processors; wherein at least one of said connectors passes through said chassis.

9. A device according to claim 8 wherein said first signal processor is 10 a pre-amplifier that is arranged to amplify a signal from said read head.

10. A device according to either of claims 8 or 9 wherein said chassis has a recess therein in which said first signal processor is located.

15 11. A device according to claim 10 wherein said recess has a conductive cover that is in electrical contact with said chassis.

12. A device according to claim 11 wherein said cover is a ground plane of a printed circuit board upon which said first processor is 20 mounted.

13. A device according to any one of claims 8 to 11 wherein said recess is located in a face of said chassis adjacent said data read head.

25 14. A device according to any one of claims 8 to 12 wherein there is provided a heat conductive pad arranged to contact both said chassis and said first signal processor so as to provide a thermal pathway from said signal processor to said chassis.

30 15. A data reading device comprising a data read head for reading data from a data storage medium, an electrically conductive chassis arranged

to at least partially enclose said data storage medium; a first signal processor; a first connector for connecting said read head to said first signal processor; a second signal processor; a second connector for connecting said first and second signal processors; an electrically 5 conductive cover, and wherein said chassis defines a recess adjacent said read head and said first signal processor is located in said recess in said chassis, said electrically conductive cover extending over said first signal processor and being in electrical contact with said chassis so as to substantially enclose said first processor, and wherein said second 10 connector passes through said chassis.

16. A method of manufacture of an electronic device comprising the steps of: i) attaching a circuit element to a conductive chassis plate; and 15 ii) connecting said circuit element to a signal processor via a passageway through said plate.

17. A method of reducing inductance of a signal carrier in a data ... reading device comprising: 20 i) connecting a signal carrier to a read head; and ii) connecting said read head to a signal processor via a passageway through a chassis plate.

18. A method of screening a signal processor of an electronic device 25 comprising the steps of: i) providing a recess in an electrically conducting chassis of said device; and ii) placing said processor in said recess.

19. A method according to claim 18 comprising: i) at least partially covering an opening of the recess with an electrically conducting cover; and ii) electrically contacting the cover to said chassis.

20. A method of screening a processor of an electronic device from electromagnetic interference by housing said processor in a recess defined in a metal support plate, which support plate also mounts other electrical components of said device.

21. A method according to claim 20 comprising enclosing said processor in said recess by covering said recess with an electrically conductive cover.