A system for determining number of cars within a train consist includes one or more cars, at least one automatic train controller (ATC) for the one or more cars, and a train line spanning the consist. Each car comprises a frequency generator and a frequency modifier. Each frequency modifier in each of the one or more cars is adapted to receive an input signal at an input frequency and generate an output signal at an output frequency different from the input frequency. A frequency generator in at least one of the cars provides a predetermined input signal at a predetermined input frequency to the frequency modifier in the at least one car when the at least one car is designated as a lead car and at least one frequency modifier in at least one of the one or more cars provides its output signal to the train line.