Product description DC 48V to DC 5V Buck Power Converter 5A/10A/15A/20A Step Down Voltage Regulator Product Wiring Instructions The red cable at the input end connects to the positive "+" terminal of the power supply. The black cable at the input end connects to the negative "-" terminal of the power supply. The yellow cable at the output end connects to the positive "+" terminal of the device. The black cable at the output end connects to the negative "-" terminal of the device.