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Electric watch
In horology the term electric watch is used for the first generation electrically-powered wristwatches which were produced beginning in 1957,〔Engineering time: inventing the electronic wristwatch, Carlene Stephens and Maggie Dennis, British Journal for the History of Science, Vol. 33, pp. 477-497, 2000, Cambridge University Press〕 before the commercial introduction of the quartz wristwatch in 1969 by Seiko with the Astron. Their timekeeping element was either a traditional balance wheel or a tuning fork, driven electromagnetically by a solenoid powered by a battery.〔THE ELECTRIC WATCH REPAIR MANUAL, Henry B. Fried, 1965, B. Jadow and Sons Publishers, Library of Congress Card Number 65-18620, p.34, "ELECTRIC TIMEPIECES - HOW AND WHY THEY WORK"〕 The hands were driven mechanically through a wheel train. They were superseded by quartz watches, which had greater accuracy and durability due to their lower parts count. Recent automatic quartz watches, which combine mechanical technology with quartz timekeeping, are not included in this classification.
== Weaknesses ==
A weak point in early balance wheel electric watches was the switch contacts on the balance wheel, which turned the solenoid on briefly to provide the impulse to keep the wheel oscillating. These wore out and did not operate reliably.〔THE ELECTRIC WATCH REPAIR MANUAL, Henry B. Fried, 1965, B. Jadow and Sons Publishers, Library of Congress Card Number 65-18620, p.59, "SPARKING: ITS CAUSES AND CURES"〕 Later designs used electromagnetic sensing, with a transistor in the circuit to turn the solenoid on.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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