Product description NWANSI DC 36V/48V to 24V Auto Buck Power Converter, 40A/50A/60A 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 connects to the negative "-" terminal of the power supply and the negative "-" terminal of the device. The yellow cable at the output end connects to the positive "+" terminal of the device.