Signal output device

A signal output device (5, 105, 205, 305, 405, 505) is provided in a communication appliance (2) which communicates with another communication appliance (3) using a single wire (4). A signal output unit (6, 106, 206, 306, 406, 506) outputs, for a prescribed signal serving as an arbitrarily defined signal, a signal obtained by means of the pass characteristics of a first filter (9) employing a Bessel filter, and a second filter (10, 12) employing a Chebyshev filter or a Butterworth filter. A cutoff frequency (fa) of the first filter is set to be lower than a cutoff frequency (fb, fc) of the second filter.