An on-board instrument to be mounted on a train, the on-board instrument comprising: a variable terminal group including one or more first terminals each usable as an input terminal or an output terminal and one or more second terminals each usable as an input terminal; a switching unit configured to switch the first terminals to the input terminal or the output terminal; a setting unit configured to control the switching unit on a basis of an instruction signal indicating the number of first terminals to be used as the output terminal, and if at least one of the first terminals is used as the output terminal, output a first signal to the first terminal that is used as the output terminal via the switching unit; and a storage unit configured to store a second signal value and a third signal value, the second signal value being a signal value of a second signal input from the input terminal, the third signal value being a signal value obtained by arraying a plurality of the second signal values on the basis of a first signal value that is a signal value of the first signal, wherein the setting unit is configured to read the second signal value or the third signal value from the storage unit on the basis of the instruction signal, and acquire information on the signal value of the second signal input, wherein the storage unit includes: a first storage unit configured to store the second signal value, the first storage unit being configured to store the signal value of the second signal of a number of bits, the number being equal to the total number of first terminals and second terminals of the variable terminal group; and a second storage unit configured to store the third signal value obtained by arraying the second signal value stored in the first storage unit at a position designated by the first signal value, and on the basis of the instruction signal, the setting unit is configured to read the second signal value from the first storage unit or read the third signal value from the second storage unit. a variable terminal group including one or more first terminals each usable as an input terminal or an output terminal and one or more second terminals each usable as an input terminal; a switching unit configured to switch the first terminals to the input terminal or the output terminal; a setting unit configured to control the switching unit on a basis of an instruction signal indicating the number of first terminals to be used as the output terminal, and if at least one of the first terminals is used as the output terminal, output a first signal to the first terminal that is used as the output terminal via the switching unit; and a storage unit configured to store a second signal value and a third signal value, the second signal value being a signal value of a second signal input from the input terminal, the third signal value being a signal value obtained by arraying a plurality of the second signal values on the basis of a first signal value that is a signal value of the first signal, wherein the setting unit is configured to read the second signal value or the third signal value from the storage unit on the basis of the instruction signal, and acquire information on the signal value of the second signal input, wherein the storage unit includes: a first storage unit configured to store the second signal value, the first storage unit being configured to store the signal value of the second signal of a number of bits, the number being equal to the total number of first terminals and second terminals of the variable terminal group; and a second storage unit configured to store the third signal value obtained by arraying the second signal value stored in the first storage unit at a position designated by the first signal value, and on the basis of the instruction signal, the setting unit is configured to read the second signal value from the first storage unit or read the third signal value from the second storage unit. a first storage unit configured to store the second signal value, the first storage unit being configured to store the signal value of the second signal of a number of bits, the number being equal to the total number of first terminals and second terminals of the variable terminal group; and a second storage unit configured to store the third signal value obtained by arraying the second signal value stored in the first storage unit at a position designated by the first signal value, and on the basis of the instruction signal, the setting unit is configured to read the second signal value from the first storage unit or read the third signal value from the second storage unit.