PURPOSE: To reduce generation of noises caused by stray capacity of flexible conductors and to prevent erroneous operation of logics by providing grounding through resistors at least at one point of a flexible conductor.

CONSTITUTION: The connection point of a collector of a transistor 12 for switching and a flexible cable 15 is grounded through a resistor 16. Because of the above resistor 16 even in case in which the transistors 10 and 12 are concurrently turned 'OFF' and electric charges are accumulated due to stray capacities C1 and C2, the charges are grounded through a bypass. Therefore, even at the point of time when the transistor 12 for switching is transferred from 'OFF' to 'ON', a larger common mode noise is not generated on the ground side. Additionally, notwithstanding where the resistor 16 may be inserted for installation, as long as it exists in the area between the flexible conductor 15 and the ground, the bypass effect of charges due to stray capacity may be obtained.