QUOTE: Originally posted by cacole What they mean is that there must be no electrical contact between the motor and locomotive frame. The motor brushes are the contacts where the wires are soldered to the back of the motor, or, if is a Bachmann or similar locomotive with a split frame, there will be long bronze contacts on the sides of the motor that touch the frame halves. You must get access to either the wires soldered to the motor or those bronze contacts and remove the wires or cut the contacts short. Then take an Ohmmeter and measure the resistance between a motor brush and the locomotive frame. It should read Infinity. If you get a reading of zero Ohms, then the motor is not isolated from the frame and you must figure out how to do so. I would suggest that you find someone with electronics experience to help you if you don't know how to isolate the motor, because you can quickly turn a decoder into a smoke generator if you connect it up wrong. If your locomotive is a newer one with the NMRA decoder socket in it, then the motor is already isolated and you don't need to worry about this aspect of decoder installation. Depending on locomotive brand, you may need to change some light bulbs or add resistors to the light circuits.