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The present invention relates to a portable electronic system and in particular to such a system which is usable in a hostile environment.
Portable electronic systems such as laptop computers are well known. Ranges of such systems are available in which all systems within the range are based on a common main unit or "host" unit. A particular model within the range is produced by customising the common host unit by connecting to it customised circuits or generally available circuits which when combined with the host unit deliver the required functionality. The customised or generally available circuits are produced on cards which can be readily plugged in to one or more connectors provided in the host unit.

Whereas in relatively large desktop computers it is often the case that the host unit is provided with internal edge connectors for receiving expansion cards, portable electronic systems such as laptop computers generally are not provided with the capability of accepting expansion cards to provide customised functionality other than through a docking station, that is an external connector into which the expansion card can be directly plugged. Portable computers may support a number of expansion card receiving slots and thus a desired functionality can be readily achieved by supplying to the user the appropriate expansion card or cards. The resultant host unit and expansion card assembly represents a perfectly acceptable solution when the electronic system is being used in relatively benign conditions, for example in an office environment, but there are many circumstances in which portable electronic systems must be ruggedised to enable their use in a hostile environment such as an automotive service facility.
For an electronic system to be acceptable in an automotive service facility, it must be sufficiently rugged to survive being dropped onto concrete from a height of as much as one metre, must be able to prevent the contamination of its circuits if the system is exposed to liquid or dust, and must be resistant to chemicals such as petrol, oil and caustic substances. It is simply not possible to provide the required ruggedisation using a conventional host unit with a docking station to receive expansion cards.

A further problem in the automotive service facility environment is that it is often desirable to provide an external cable to enable an expansion card to be directly connected to equipment under test. For example a digital multi-meter requires external probes. Readily available expansion cards (generally referred to as third party cards) are available at low cost which can provide the required functionality but they are provided with relatively fragile external cables which could not withstand the rigours of the automotive service environment. Connections between such cables and the expansion cards are also not sufficiently rugged as to provide adequate protection against contamination.
Portable electronic systems are available which are sufficiently rugged to withstand use in an automotive service environment. The known systems comprise a host unit the functionality of which can be determined by connecting to it any one of a range of customised expansion units. The expansion units are however custom-built with the necessary electronic components mounted on a card which is incorporated in a rugged enclosure, the components being connected to the external environment via a rugged external connector. Such an approach is expensive to implement as the supplier must manufacture and maintain stocks of each of the customised expansion units. In particular it is not possible for the supplier to make use of the wide range of readily available third party expansion cards.
It is an objection of the present invention to obviate or mitigate the problems outlined above.
According to the present invention there is provided a portable electronic system comprising a host unit and at least one expansion card which is plugged into the host unit to determine the functionality of the electronic system, the said at least one expansion card comprising a connector through which the expansion card is to be coupled to at least one signal source external to the electronic system, wherein the host unit is mounted in a body and said at least one expansion card is mounted in a card carrier which may be mounted on the body, the carrier including an interface connected to the said at least one expansion card and connecting the said at least one expansion card to the host unit when the carrier is mounted on the body, the carrier defining at least one external connector coupled to the connector of the said at least one expansion card, and the body and carrier when the carrier is mounted on the body together defining a rugged enclosure for the host unit and the said at least one expansion card.
The invention makes it possible to use standard PC cards which can be readily plugged in to the interface in the card carrier. An expansion card connector which will generally be connected to a short length of cable can then be connected to the external connector of the card carrier by plugging the expansion card connector into a transition connector coupled to the external connector. The card carrier can be delivered to the user as a sealed unit, the card carrier interface being automatically plugged into the host unit when the card carrier is mounted on the host unit. The expansion cards can then communicate with the external environment through the external connector of the card carrier unit and with the host unit via the interface into which the expansion card is plugged. The overall structure can be readily ruggedised by appropriate design of the external connector of the card carrier and the characteristics of an enclosure formed when the card carrier is mounted on the host unit by the contribution of a casing of the host unit and a casing of the card carrier.
A host unit with basic functionality can be delivered to the end user with a removable rear panel. If the functionality of the host unit is to be modified, the rear panel can be simply removed to expose an interface of the host unit. The system supplier will then deliver a card carrier unit in sealed form incorporating the appropriate expansion cards and rugged external connectors. The user then simply secures the card carrier to the host unit, thereby connecting the interface on the card carrier to the interface of the host unit. Subsequent modifications of functionality can be achieved simply by replacing one card carrier with another.
An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which;
Figure 1 is a perspective front view of an automotive tester system incorporating the present invention;
Figure 2 is a view from above and behind of the system shown in Figure 1 with a support leg shown in the stowed position; and
Figure 3 is a schematic illustration of a PC card carrier incorporated in the system illustrated in Figures 1 and 2.

Referring to Figures 1 and 2, the illustrated device has a ruggedised casing 1 supporting a foldable rear support 2. A display screen 3 enables a user to display information gathered by the unit, and control buttons 4 enable the user to exercise appropriate control of the unit. A handle 5 makes the unit readily portable.
The rear of the unit supports a card carrier 6 which is maintained in position by screws 7 and defines three external rugged connectors 8. All input and output signals from the unit are delivered through one or more of the rugged connectors 8.
The rectangular card carrier 6 which is held in engagement with the rear of the unit by the screws 7 may be removed and replaced either with a simple cover defining no more than a connector or by a replacement card carrier. Circuits determining the overall functionality of the unit are incorporated in this removable component and connected to the external connectors 8 as schematically illustrated in Figure 3.
Referring to Figure 3, all the illustrated components are mounted in the removable card carrier 6. The removable card carrier 6 is represented schematically by the rectangle 6 in Figure 3 and supports the external rugged connectors 8 (only two are shown in Figure 3 rather than the three of Figure 2) and a PC card interface 9 which may be connected as schematically represented by arrow 10 to a mating interface provided in the host unit casing 1. The interface 9 will incorporate PC card electronics as well as appropriate connectors. Standard PC cards 11 are plugged directly into the interface 9. Cables 12 from the PC cards 11 are coupled to transition connectors 13 which in turn are coupled by internal cables 14 to the external rugged connectors 8.
A device such as that schematically illustrated in Figure 3 can be readily manufactured using standard casing and interface components, readily available standard PC cards and readily available external rugged connectors. New functional requirements can be rapidly satisfied using readily available components without any customised design effort. The various components can be readily encapsulated in appropriate casing components and delivered to the end user in a ruggedised form such that the readily available standard components are completely embedded inside the card carrier. Once that card carrier is mounted on the host unit all of the components are effectively embedded within a common rugged enclosure.

Although in the illustrated embodiment the required functionality is achieved using PC cards it will be appreciated that alternative circuits could be used, for example PCMCIA and Cardbus technology. The invention may be implemented on a Pentium based PC, but the invention is equally applicable to other systems, for example RISC architectures and 68000 derivative systems.
The components used can be readily selected to suit the requirements of the target environment. Components embedded in the card carrier can be supported and encapsulated as necessary to meet the target requirements. Thus a diversity of third party PC card devices may be used even though they have been designed for use in an office environment. The functionality of the selected PC cards is embedded into the overall system and the external connections are simply adapted as necessary to the target environment.