Accoring to Eddie Izzard, a 'turny-dial system' is a control mechanism for appliances that, despite having numerous settings, can only really be in two states - low and high. Needless to say, neither of these states is particularly useful.

Showers have such a system, especially the ones in shower blocks on campsites. They can either be very hot, or exceedingly cold - but never comfortably warm. Toasters too have a similar system producing, unless watched carefully, either warm bread or charcoal - never, ever edible toast.

'Turny-dials' lie to us.