page_title: Electricity on Shabbat
section_title: Shabbat clocks
hierarchical_section_title: Electricity on Shabbat / Ways of circumventing the Shabbat prohibitions / Shabbat clocks
caption_attribution_description: עברית: שעון שבת
context_page_description: Many Jews who strictly observe Shabbat refrain from using electrical devices on Shabbat, with the exception of passive enjoyment of devices which were set up before Shabbat. Various rabbinical authorities have pronounced on what is permitted and what is not, but there are many disagreements in detailed interpretation, both between different individual authorities and between branches of Judaism.
  In Orthodox Judaism, it is agreed that electrical devices may not be used on Shabbat, but Orthodox authorities of Jewish law have disagreed about the basis of this prohibition since the early 20th century. Many Orthodox leaders have held that turning on an incandescent light bulb violates the Biblical prohibition against igniting a fire. However, the reasons for prohibiting the operation of an electrical appliance that does not involve heating metal to glowing temperatures, are not agreed upon. At least six substantive reasons have been suggested, and a minority believe that turning on most electrical appliances is prohibited only because of common Jewish practice and tradition and to maintain the spirit of Shabbos, but not for any substantive technical halachik reason.
context_section_description: In general, halacha permits a Jew to begin a Shabbat-violating action on Friday (before Shabbat) even though the action will be completed automatically on Shabbat. Therefore, the consensus of contemporary authorities permits a Jew to program a timer (referred to as a "Shabbat clock") before Shabbat to perform automatically a prohibited action on Shabbat. For example, it is permitted to attach a timer to a light switch on Friday afternoon so that the light will turn off late on Friday night when people wish to sleep, and will turn on again the next day when people are awake.
  However, an exception to this rule may be the production of a noise which disturbs the peaceful environment of Shabbat, as shown by a debate in the Talmud over whether a Jew may add wheat on Friday to a water mill that will run automatically on Shabbat, because the addition of wheat to the mill will cause a loud noise. Rishonim disagree as to which opinion is normative. Joseph Caro in the Shulchan Aruch permits this action, but Moses Isserles (the Ramo) prohibits it absent great need. Accordingly, Rabbis Moses Feinstein and Shlomo Auerbach prohibit programming a radio to turn on during Shabbat, or allowing it to run on Shabbat, not because of the violation of electricity as such, but rather because the noise of the radio violates a separate prohibition.
  Some authorities have raised other reasons to prohibit Shabbat clocks in general, but the consensus of many rabbis permits their use. Nowadays they are commonly used to manage lights in private homes, to operate dishwashers and milk cows in Shabbat-observant kibbutzim and moshavim, and for various purposes in public facilities such as hospitals and hotels.
caption: A Shabbat clock. Each orange peg determines its state for one 15-minute interval. This clock is set to turn on a light between approximately 17:00 and 23:30 (the light would be plugged into the 3-prong Israeli socket).
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