You need to connect a resistor 1K(1000ohm) 1/4Watt or 1.5K(1500ohm) 1/8 Wattother valuein series when you use the function wires with LED to limit the current of led.

(Caution) DCC Voltages. Please make sure your DCC Voltages are less than 16V. We
recommend track voltage at 12V. Read below to understand all about dcc voltage. Over
Voltage may make the decoder irreparable harm. We do not accept dispute if your voltage is over 16V and burn the decoders. If your track voltage can not lower to 16V, please not order our decoders.

http://www.sumidacrossing.org/ModelTrains/ModelTrainDCC/DCCDecoders/DCCVoltages/

Plux16 (NEM 658) Dcc decoders

Interface: Plux16 + Blue and Black Wire
Scale: HO Scale
Size:16mm*17.5mm*3mm
Current Rating: 1A
Function: 4*100mA
Support to connect with KungFu stay alive kits