Changing gear with the Wilson box relied on the control of the brake bands that held each epicyclic's annulus in fixed position. The brake band to be selected was controlled by a rotating cam, moved by the gear shift lever. Only one band was engaged for each gear selection. This small hand-operated lever could not provide enough power to engage and lock the brake band, thus the need for the foot pedal. The actual movement of the brake bands was controlled by the 'toggle' mechanism, a distinctive feature of the Wilson design. When the pedal was pressed and released, a series or 'busbar' of finger-like levers were pressed upwards by a strong coil spring, against a series of light linkages or 'operating struts'. The position of each linkage was controlled by the gear selection camshaft. If the cam (for each gear) held the linkage in place, rather than allowing it to swing out of the way, the busbar finger would then press, via the operating strut, onto the toggles controlling the brake bands themselves. These toggles provided the additional leverage necessary to hold the brake band in place, under the force of the coil spring, until the pedal was next pressed. A further characteristic of the Wilson design was the use of self-adjusting nuts on each band, to compensate for wear. The action of engaging and disengaging each band was sufficient to advance the ratchet nuts and so adjust for wear by taking up any slack.