Product description NWANSI DC 8V-100V to 5V, 17V-100V to 12V 2A/3A Step-Down Power Converter 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.