Transmission line type components (1, 1'), which form coaxial lines having a very low characteristic impedance by coaxially installing a cylindrical outer conductor made of a conductive material being larger in diameter than an inner conductor so as to cover via a high dielectric insulating material the surface of an inner conductor made of a conductive material, are inserted in series between a power supply line (8) and a ground line (9) connected with a dc source on a printed circuit board and an I.SI (6) power supply port, whereby almost the entire high-frequency power supply current generated from the I.SI (6) is reflected off the I.SI (6) power supply port, and part of the high-frequency power supply current intruding into the components (1, 1') is consumed and does not reach the external power supply line (8).