In the present invention an output terminal (23) of a signal output device (20) is connected via a branch path (33) to a voltage division point (D) provided in the middle of main trunk paths (31, 32) connecting a power supply terminal (21) and a ground terminal (22), and transmits an output signal based on the voltage of the voltage division point (D) to the outside. A signal generation circuit (60) adjusts the voltage of the voltage division point (D) and generates the output signal. A short-circuit detection circuit (50) detects a short-circuit between the output terminal (23) and the other terminals when a current flowing in the branch path (33) is greater than a prescribed short-circuit detection threshold value. When a short-circuit is detected by the short-circuit detection circuit (50) switching circuits (61, 62) switch the conduction capacity or the configuration of the signal generation circuit (60), thereby limiting the short-circuit current flowing in the branch path (33). The short-circuit current is set to a value equal to or greater than the short-circuit detection threshold value and less than an upper limit current value based on the supply capacity of a direct-current power supply.