The authors have measured the series resistance of two ballistic resistors, or quantum point contacts, in two configurations. First when the resistors are collinear they measure the series resistance and the intermediate voltage between the resistors. Using a simple model they calculate the ballistic transport coefficient from the data. They find that the highest values are obtained when one channel is much wider than the other. Poorest transmission is always obtained when the two channels are identical. Secondly, they investigate two quantum point contacts perpendicular to each other. They find that in zero field the resistances add classically but that the transmission coefficient increases if either the magnetic field or the width of the constriction in the ballistic resistors is increased.