An apparatus in which an outer conductive ring surrounds the periphery of a touch-sensitive surface of a touch sensor serving as a manually-operable control, wherein a portion of the outer conductive ring is also between the touch-sensitive surface and another manually-operable control that lacks the ability to sense the mere touch of a tip of a digit of a user. A processing device causes the level of capacitance of the outer conductive ring to be measured on a recurring basis for instances of an amount of additional capacitance above a minimum capacitance threshold, and employs such amounts of additional capacitance in a comparison to distinguish between the user interacting with a control surface defined on the touch-sensitive surface of the touch sensor or the other manually-operable control.