Hi
You need to get the Murphy Models specific 121 non sound decoder for your 121 .
This decoder is set up specific for 121 only and will give all the required functions that are required for the 121 .
Unless you have DCC knowledge of Mapping functions using the Lok programming / Decoder Pro with a Sprogg then I would suggest that you spend the extra euros , buy the specific decoder and enjoy your Murphy's 121 .
You can use your Lok Pilot decoders on your Murphy Models 181.
Enjoy