On-board instrument, signal output device, on-board instrument setting system, and signal value information acquisition method

First terminals are usable as input terminals or output terminals and second terminals are usable as input terminals. A switching unit switches the first terminals between input and output, based on an instruction indicating the number of first terminals to be used as output terminals. If at least one first terminal is used as an output terminal, a first signal is output to the first terminals used as output terminals. A storage unit (stores second and third signal values, the second signal value being a value of a second signal input from the input terminal, the third signal value being a value obtained by arraying a plurality of the second signal values based on the value of the first signal. A setting unit reads the second signal value or the third signal value based on the instruction signal, and acquires information on the value of the second signal input.