Impedance matching can perhaps be explained by comparing the pulse traveling down the cable to water flowing through a pipe. Imagine a section of pipe, one inch in diameter, welded to a section of pipe, one half inch smaller in diameter. If water were to flow through these welded pipes the change in diameter would cause a disturbance in the flow. In the same manner, a cable with mismatched impedance would create a disturbance in the ‘flow’ of the signal. The disadvantages of not having a matched system are: the pulse does not reach the output; and increased noise.