The free end motion of the C-Bourdon tube is insufficient to operate some of the motion balance devices, such as the transmitters. The spiral element shown in Figure 5.4f is essentially a series of C-Bourdon tubes joined end to end. When pressure is applied, this flat spiral tends to uncoil and produces a greater movement of the free end, requiring no mechanical amplification. This increases the sensitivity and accuracy of the instrument because no lost motion or friction is introduced through the links and levers.