Abstract: A supporting plate having a network of conductors, on which supporting plate a number of circuit components are placed which are interconnected in the network of conductors in an electric circuit. In a place of the circuit which is sensitive to moisture, a board opening is provided in which a member of a minimum moisture-absorbing material is fitted. The connections of the surrounding circuit components extend in an aperture of the member and are electrically interconnected there. The stability of the circuit is considerably improved thereby in particular in the case in which the circuit is an oscillator circuit.