Product description NWANSI DC 12V/24V to DC 5V 3A-100A Buck Power Converter, Step Down Voltage Regulator Supply Module 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.