Product description NWANSI DC 8-35V to 12V Auto Buck-Boost Converter, 2A/3A/5A/10A 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.