Position indication should be provided.
Additional Information:
Desirable alternatives are: (1) illuminated indicator lights, (2) a line engraved both on the top of the knob and down the side, or (3) a pointer shape. It should not be possible to confuse the position of the knob in reference to position markers on the panel. To minimize the problem of parallax, pointers on knobs should be mounted close to the settings to which they point.