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.