Abstract: The invention relates to electrical filters comprising piezoelectric crystals.When very considerable variations in slope are required in the transmission curve of filters of this type, it is necessary to use a plurality of crystals having very different equivalent self-inductances, some of which are impossible to obtain. The invention overcomes these limitations by using only crystals (X'.sub.1, X'.sub.2, X'.sub.3 . . . X'.sub.7) having feasible self-inductances and by establishing the desired self-inductances by using transformers such as T.sub.3.The filters according to the invention may be used in particular for the same applications as JAUMANN-type filters in telephone communications.