The SDXN146K4 decoder is a Series 6, four function decoder. The decoder already has LEDs configured as the Forward/Reverse Headlight. There are additional solder pads which will allow you to add functions F1 and F2. These functions can be programmed to suit your particular needs. The SDXN146K4 has a built in current limiter that sets output current to approximatly 10ma for the cooresponding + and - pads as shown. There is also an available Cam Input for sycronized chuffing. See the Digitrax Decoder Manual for complete function and Cam Input setup instructions.