A control board connectable to a liquid ejection head includes a power supply circuit outputting a first voltage, a connector connectable to a cable through which the first voltage is input and a second voltage is output, and a processor detecting a connection error of the cable using a difference between the first and second voltages, and control the circuit to turn off upon detection of the error. The connector includes first, second, and third terminals adjacent to each other and arranged along a direction in this order and fourth, fifth, and sixth terminals adjacent to each other and arranged along the first direction in this order. The first voltage is input to the second terminal, the second voltage is output from the fifth terminal, and the first, third, fourth, and sixth terminals are ground terminals. The second and fifth terminals are short-circuited in the liquid ejection head.