T 0475/00 (Bus system/D2B SYSTEMS) 28-06-2002

1. The invention

The invention is a local communication bus system connecting a plurality of devices. A screen is provided (output subdevice 46) on which status information about a device can be displayed. The request for displaying such information is initiated by a first control subdevice and transmitted to the device whose status is asked for. That device contains a second control subdevice which composes a "user-readable" message and transmits it to the output subdevice for display. The format of the user-readable message is specified in the request sent by the first control subdevice. It is explained in the description that the system does not need to interpret the content of the user-readable message (column 9, lines 23 to 35). This is said to have advantages, one being that a device in the system is not required to have information about other devices in order to initiate the display of a status message.

2. Construction of claim 1

2.1. The discussion at the oral proceedings before the Board centred on the expression "user-readable". The patent proprietor argued that it effectively implied that the displayed message was in a natural language (cf. column 9, lines 53 of the patent in suit). The opponent on the other hand took the view that it was hardly limiting at all since all kinds of users must be considered, including service-men who would understand system messages whatever their form.

2.2. Normally, an apparatus cannot be defined in terms of the skills of prospective users of the apparatus (cf. Rule 29 EPC: "The claims shall define the matter for which protection is sought in terms of the technical features of the invention"). It appears even less appropriate to define sub-groups of users, such as service-men, for whom the apparatus might or might not be intended. The Board therefore agrees with the opponent that a narrow interpretation of the expression "user-readable" would be inappropriate and takes the view that there is no constraint on the kind of representation on the display. It could consist of plain text, abbreviations, symbols or images, binary or hex code, etc. Still, considering the feature in the light of the description the Board finds that it is not entirely void of technical meaning. As confirmed by the description, status information transmitted by the second control device need not be converted - e.g. by means of a look-up table in the display device which associates the incoming data with predetermined text messages - in order to be displayed. This should be contrasted with the hypothetical situation that a transmitted message cannot be displayed because a converter in the display does not recognise it. For example, if the conversion were defined for certain devices only, a message composed by a different device would be lost. Whether information to be displayed is lost or not is regarded as having technical significance, following decision T 115/85 (OJ EPO 1990,030) according to which "giving visual indications automatically about conditions prevailing in an apparatus or system is basically a technical problem". Therefore, the arrangement by which the second control device composes "user-readable" messages is regarded as a technically limiting feature of the claimed bus system.

3. Inventive step

3.1. The opponent has argued that E2, describing the "Dimensia" system, anticipates the subject-matter of claim 1 as granted (ie the features of the pre-characterising portion of claim 1 now under consideration) and renders the invention obvious. According to E2 an interrogated device sends a status message which "can be as long as 16 bytes in length... The status information can include numbers such as counter values, current band numbers, time remaining, etc. The status is then displayed on the screen" (page 68, bottom of 3rd column). The opponent understands the indication "as long as 16 bytes" in the way that the message could also be shorter, something which the initiating device would have to specify in the device information request message (cf. the characterising portion of claim 1).

3.2. The patent proprietor is of the view that the status message in E2 is not "user-readable". Instead, the status message must be assumed to be converted into a message to be displayed, as indicated at the end of page 69: "Tasks related to system operation include... converting status from system components to on-screen display messages...". The 16 byte format mentioned in E2 was thus not in respect of a user-readable signal. The format of the message actually displayed was not at all described.

3.3. On this point the Board agrees with the patent proprietor. It appears that E2 can indeed be understood in the way that the transmission from the interrogated device is replaced by a message which is displayed, and it is not clear what would happen if the transmitted bytes were not recognised by the system. It follows that the feature "user-readable" (in the meaning of the patent in suit, see point 2.2 above) is not clearly and unambiguously disclosed in E2. Nor is it an obvious addition. If the technical aim is seen as avoiding the need for devices to be informed about other devices of the system (cf. point 1 above), E2 does not mention it. It is true that the importance of "future compatibility" and "maximum utility with future Dimensia components" is emphasised, but these goals seem to be achieved chiefly by means of "uniform formats" (page 66, first two columns). This is very general and might merely imply that devices should be compatible (at some level).

User-readable messages can be expected to be comparatively long, which means that they would only be transmitted over the bus if the skilled person saw a good reason for doing so. In the absence of such a reason the invention according to claim 1 must be regarded as involving an inventive step.

3.4. The opponent has argued that any electrical signal from a device would have to be converted in order to be displayed, also the "user-readable messages" according to the invention. This is naturally not denied. Important is however the kind of conversion employed. If any status signal is such that it can be converted and displayed (in whatever form) without loss of information, then the messages are user-readable. But if only a limited number of signals can be processed, e.g. because the on-screen display messages are predetermined (which could be the case in E2), the status signals are not generally user-readable.

3.5. The opponent has furthermore pointed to column 2, lines 34 to 43 of the patent in suit, where it is stated that the initiating subdevice may "combine or substitute the user message from the addressed control subdevice with user messages of its own and/or user messages acquired or received from further addressed control subdevices, and transmit the combined user message to the user output subdevice for display". In the opponent's view this passage shows that messages from interrogated devices may be replaced, just as they appear to be in E2, so that there is in fact no difference between the invention and this prior art. This argument is however not found to be convincing. According to claim 1 the second control subdevice is "arranged to compose a formatted user-readable message". This is an apparatus feature and independent of the final fate of the message. In other words, even if a user-readable message is replaced, it was still composed in such a way that it would have been suitable for display. In E2, however, it is not apparent that the status transmissions can be displayed at all unless they are replaced by on-screen display messages.

3.6. As to document D1, the opponent has not argued that the invention would be rendered obvious by this document. Still, some comments on D1 might be appropriate. This document concerns a communication bus system capable of displaying certain status information to the user, such as "VTR ON" (see Figure 6A). This message does not originate in a subdevice but is the result of a conversion of a string of hex code generated by a subdevice. This is in fact the kind of prior art on which the invention is intended to improve (cf. the patent in suit, column 1, line 25 to column 2, line 12). If however the hex code for some reason cannot be converted, it is displayed as it is (Figure 7B). The Board accepts the opponent's view that this case corresponds to the display of a formatted user-readable message composed by a control device, as set out in the pre-amble of claim 1. But since the hex code is not the desired output, the skilled person would have had no reason to permit the (requesting) first control subdevice to specify its format. Therefore D1 does not suggest the characterising portion of claim 1.

3.7. It follows that claim 1 is acceptable. Independent claim 8, directed to an apparatus for use as an addressable device in such a bus system, is allowable for the same reasons.

4. The patent proprietor's auxiliary request

Since the Board finds that the patent should be maintained in the version upheld by the Opposition Division there is no need to consider the patent proprietor's auxiliary request for maintenance in a more limited form.