you need a booster, not a resistor to program certain sound decoders. The booster is only needed for QSI, MRC, Soundtraxx, Loksound, and Digitrax sound decoders. Regular decoders without sound do not need the booster. Broadway Limited Blueline does not need the booster and will not program if a booster is used.
The booster should be on a toggle switch so that it can be turned on and off as needed.