The present invention provides a method of producing a resistance element incorporated in a printed circuit board at an accuracy of resistance value of \xb11% or less, at low cost and with a good yield while the resistance element formed by a resistor paste is incorporated. The outer housing is so formed that a centerline of a connector opening and a centerline of a waterproof plug receiving portion are offset a predetermined amount from each other, and the density of wires in the sealing material-filling space within the outer housing is made generally uniform. N virtual JTAG test access ports, each having an input and an output. A holding fixture holds the foldable portion in the desired optical coupling orientation.