This heading covers devices which do not have the character of clocks of heading 91.05, but are mainly designed to make or break electric circuits automatically at given times, usually at times determined according to a previously established daily or weekly programme. To be included in this heading these devices must have a movement of the watch or clock type (including secondary or synchronous motor clock movements) or a synchronous motor with or without reduction gear.
Time switches are used for the control of lighting circuits (for public places, shop windows, staircases, illuminated signs, etc.), heating circuits (water heaters, etc.), cooling installations, pumps, two-rate electricity supply meters, etc. They consist essentially of a mechanical or electric movement of the watch or clock type or a synchronous motor, usually a dial with or without hands, a time-regulating device (levers and pins), together with systems of driving relays, switches and commutators. The whole is enclosed in a case with terminals. The dial is usually marked in hours and sometimes also in days and months; levers or pins around its periphery actuate the contact devices at the desired times.
Time switches may be set in action by thermostats, pressure regulators, water level regulators, etc.
The heading also includes switches for making and breaking the circuit supplying electrical apparatus (television receivers, irons, washing machines, billiard table lights, etc.), switching on when coins are inserted and switching off through the action of a synchronous motor, the interval being determined by the number of coins inserted.
The heading excludes the following when presented separately : cases for the devices described above (classified either in heading 91.12 or in their respective headings, see the Explanatory Note to heading 91.12), watch or clock movements (headings 91.08 to 91.10) and parts of such movements (generally heading 91.10 or 91.14).
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