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T 174/21 – Sufficiency of disclosure: “One way” vs. “over the whole scope claimed” – Ex officio examination by a board

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The patent relates to a method of processing a signal in a hearing instrument, and to a hearing instrument, in particular a hearing aid.

Brief outline of the case

The opposition was rejected and the opponent appealed.

The board of appeal considered that the invention could not be enabled over the whole range claimed. The same applied to AR 1-7. The patent was eventually revoked.

The board held that

  • there was a disclosure of “at least one way” but not over the “whole scope claimed
  • it was entitled to raise objections ex-officio.

The decision is interesting in view of those two points.

The OD’s point of view

The OD considered the opposed patent specified “at least one way” to carry out the method of claim 1 and hence sufficiency was given.

The proprietor’s point of view

With reference to T 2773/18, the proprietor expressed some doubts as to the applicability of the “whole range claimed“-requirement in the field of audiology.

The proprietor was of the opinion that the board, as a judicial body, should refrain from bringing ex-officio the objection “applicability over the whole range”. Accordingly, it requested the board not to pursue this issue or to remit the case to the opposition division to decide on it first.

The proprietor argued that the lack of sufficiency was only substantiated by suggesting that the “acoustic signal” and the “frequency-dependent ear-independent reference characteristics” according to feature (c) alone were not sufficient to determine the “ear-canal impedance” in accordance with that feature.

The board’s decision

For the board, disclosing one way does not mean that the opposed patent discloses the subject-matter of claim 1, in a manner sufficiently clear and complete for it to be carried out by the skilled person.

This is only the case if the “at least one way” covers, possibly augmented with the skilled person’s common general knowledge, the “whole range claimed“. The board referred to T 867/21, Reasons 3.2.

However, the board considered that doubts as to the applicability of the “whole range claimed”-requirement in the field of audiology were unfounded. The board referred in this respect to the conclusions drawn in T 149/21 (Reasons 3.4 and 3.6).

General considerations about audiology

The board considered that there are several influences (“acoustic leakage”, dampening by the ear canal as such, possible contaminations of the ear canal) that can impact the signal at the eardrum of the person wearing the hearing aid.

The board concluded that it is not always possible to measure the acoustic pressure at the eardrum. In those cases, the amplification characteristic of the hearing instrument is often measured outside the ear with a tube, “coupler”, connected to the receiver output. This tube simulates the ear canal.

In particular feature (c) was a key feature. Feature (c) reads: “determining, from the acoustic signal and from a frequency dependent ear independent reference characteristics of the hearing instrument, an ear canal impedance”.

Sufficiency of disclosure over the whole range claimed

With regard to feature (c) of claim 1, in order to be able to carry out the claimed invention over the whole range claimed, the skilled person in the field of hearing aids must in fact select a suitable “frequency-dependent ear-independent reference characteristic of the hearing instrument”.

This has to be done to determine the respective “ear-canal impedance” in order to then be able to calculate the “estimate of the acoustic transfer quantity” in accordance with feature (d).

The claimed method of “estimating an acoustic transfer quantity representative of a sound pressure transfer to the eardrum of an ear” cannot be carried out for all kinds of frequency-dependent and ear-independent reference characteristics encompassed by feature (c).

In particular, a “microphone characteristic” constitutes one example of a hearing-instrument characteristic that is frequency-dependent and ear-independent but for which the claimed method cannot be carried out.

This is because a microphone characteristic will typically bear no information on how the ear canal actually impacts incident sound. Such information is however crucial when determining the “ear-canal impedance” in accordance with feature (c). As a result, a “microphone characteristic” cannot be used to carry out the method defined in claim 1.

Ex-officio objection

From a substantive point of view, the proprietor did not convince the board that the issue was “entirely new”. This is because the “determining” step in accordance with feature (c) of the “ear-canal impedance” by means of the “frequency-dependent ear-independent reference characteristics of the hearing instrument” was already challenged regarding sufficiency of disclosure in the first-instance proceedings.

Iin the board’s view, the proprietor was informed that the “determining” step in accordance with feature (c) was potentially of a contentious nature. By providing this additional argument ex officio, the board merely illustrated its contentious nature by drawing upon its technical expertise to provide a concrete example of a “frequency-dependent ear-independent reference characteristics” in accordance with feature (c) for which the “determining” step according to this feature is not sufficiently disclosed.

Procedural aspects

From a procedural point of view, the board was not aware of any provision of the RPBA which could and would limit the powers and the duties provided for in Articles 114 and 111(1), respectively, in appeal proceedings.

The same applies in particular to Art 12(2) RPBA as this provision states that the “primary object of the appeal proceedings” is to “review the decision under appeal in a judicial manner”.

However, it does not limit the way in which the board is to carry out this review. Nor does it prevent the board from considering other secondary objects. Instead, this provision is primarily concerned with the obligations of the parties, not the board.

Moreover, even if a provision of the RPBA were to limit the powers and duties of the board under Articles 111(1) and 114(1) to examine or raise an issue of its own motion, such a provision would not only be “incompatible with the spirit and purpose of the Convention”, see Article 23 RPBA. It would also be inapplicable.

The RPBA as “secondary legislation”, see Article 23(4) and Rule 12c EPC, could never take precedence over the provisions of the EPC itself.  

As regards the remittal of the case to the OD, the board noted that the ground for opposition under Art 100(b) has already been considered in the contested decision. The board therefore saw no “special reasons” within the meaning of Art 11 RPBA  which could justify the proprietor’s request for remittal.


The decision reminds important points of law and procedure.

Firstly, audiology is not a technical domain in which other rules apply when it comes to sufficiency.

Secondly, “one way” of implementing an invention does not mean that the invention can be implemented over the whole range claimed.

Thirdly, Art 114(1) does not limit deciding bodies of the EPO to the facts, evidence and arguments provided by the parties and the relief sought.

With the RPBA it has become accepted practice that a board only examines whether the decision was correct and anything not discussed in first instance can be disregarded.

In the present case, the point raised by the board was contentions from the beginning of the opposition procedure, and it was normal that the board went further than the OD.

Last but not least, one should not forget that the EPO should not maintain patents which have no reason d’être.

No amendment of the EPC by secondary legislation

It is further interesting to note that the board acknowledged that “secondary legislation” can never take precedence over the provisions of the EPC itself. 

In the OP for G 1/21 (and not in the OP for G 2/21) the representatives of the president repeatedly asserted that the EPC could be amended by secondary legislation. The board has strikingly refuted this allegation.

Actually, the only mechanism of amendment of the EPC is Art 174 and for the Implementing regulation it is Art 164(1).


2 replies on “T 174/21 – Sufficiency of disclosure: “One way” vs. “over the whole scope claimed” – Ex officio examination by a board”

Confused Observersays:

It is indeed interesting to note that the board acknowledged that “secondary legislation” can never take precedence over the provisions of the EPC itself.

I agree that that implies that the only mechanism of amendment of the EPC is Art 174 and for the Implementing regulation it is Art 164(1).

But, the Enlarged Board in G 2/21 did accept that an amendment to a Rule (introduction of second paragraph in Rule 28) did results in a change of the meaning of Art.53(c), and used their so-called dynamic interpretation to effectively have an amended Art53(c).

How to understand all of this?

Avatar photoDaniel X. Thomassays:

@ Confused observer

That you were confused with my comment is the result of a typo of mine.
I have now amended the post and referred to G 1/21 and not to G 2/21.

As far as dynamic interpretations are concerned, I have some reservations, as dynamic interpretations are to much linked with the zeitgeist.

G 2/21 never mentions anything about dynamic interpretation. It is was in G 3/19 that a dynamic interpretation came up for the first time.

I apologise for my mistake and hope I could remove the confusion.

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