BALANCED TRANSMISSION IC PROTECTIVE CIRCUIT IN BALANCED TRANSMISSION DEVICE

PROBLEM TO BE SOLVED: To protect an IC from an abnormal voltage caused by an external noise when a pulse signal is transmitted in a balanced manner using the IC by connecting capacitor whose one end is grounded to each of two signal elec tric lines for transmitting the pulse signal and a simple structure. SOLUTION: In a balanced transmission device composed of a transmission driving IC 21, a pair of signal transmission lines 3 and 4 and a receiving IC 11, a series of rectangular pulse signals formed by a controller are sent to the pair of transmission lines 3 and 4 by the transmission driving circuit 21 and a pulse signal A propagated through the lines 3 and 4 is received by the receiving circuit 11. In this case, even when an abnormal voltage is generated in the line 3 or 4 because of the occurrence of thunder or the like, the voltage is discharged to the ground through capacitors 5 and 6. When the capacitance of the capacitors 5 and 6 are increased, although a reduction in impedance made for a high frequency component is effective for the prevention of the abnormal voltage, the propagated pulse signal wave shape is destroyed and thus a lighting system 1 caused to misoperate. Thus, preferably the capacitance of the capacitors 5 and 5 are set to 0.001 to 0.047μF.