Abstract: A data communication interface between a high-power device and a low-power device enabling wherein a cable having connectors at its both ends connects the high-power device and the low-power device; and the low-power device has its own incorporated level conversion circuit and drives same with a voltage which is supplied as a source voltage for the low-power device. The circuit receives a data signal at voltage levels compatible with the high-power device. The circuit converts the received signal into a data signal which is acceptable by the low-power device. The circuit receives from the low-power device a data signal at voltage levels compatible with the low-power device, and also converts the received signal into a signal which is acceptable by the high-power device. The level conversion circuit needs no element, such as a zener diode, for lowering (clamping) a voltage because the circuit is powered by the low-power device.