This invention, is concerning a signal voltage device, in which transformers 22a, 22b and a reception circuit 24 are formed on the same chip, and accordingly, no ESD protective element connected to a transformer connection terminal of the reception circuit 24 is required, and negative pulses generated in reception-side inductors 11 can be used in signal transmission. Signal transmission using both positive pulses and negative pulses is made possible as a result, and a stable signal transmission operation can be carried out even in a case where delay time varies in a signal detection circuit. Further, a reception circuit of low power consumption can be configured by using a single-ended Schmitt trigger circuit 14 in the signal detection circuit.