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E Moving coil system, contact controlled

System with the coil on the balance wheel, fixed magnets and mechanical contacts.

The most important watches of this kind are the Hamilton 500 and the Epperlein 100. Hamilton and Epperlein worked co-operatively and developed the world's first electric watch for commercial use.

Functioning of these watches will be reviewed very briefly: When an electric current flows in a magnetic field, it is affected by an electromagnetic force (i.e. Lorentz force). This is the basic principle of every electric motor. These watches have a coil fixed on the balance. At the moment the left and the right side of the coil reach inside the magnetic field of the two platinum-cobalt magnets, the contact springs are closed by a very small pin on the balance. Consequently, the electric current flows through the coil and the coil will receive an impulse from the electromagnetic force.

The following watches give the balance one impulse during each swing: Hamilton, Epperlein and UMF. A slightly different construction is used in the Laco 860, the Timex watches, the Porta Elechron and Bifora. The movements in these watches give the balance two impulses during each swing.

Not only the Western world showed interest in the development of electric wrist watches. A Russian electric watch came into production somewhere around 1962. Produced in Moscow, the 'Electritscheskye' of the state-owned watch factory Petroworjetz worked with a balance frequency of 2.5 Hz and was powered by a 1.35 V mercury cell. Unfortunately no additional information is available.

The moving coil watches with a transistorised switch system will be dealt with in a later chapter.

The early moving coil watches with contacts are:

1Hamilton 500 and 505.
2Epperlein 100.
3Laco 860 and the Timex 67, 82, 84, 85, 69, 71, 40, 41 and 42.
4Porta Elechron 1000, 1001, 1002 and 3000.
5UMF 25 and 26.


The Bifora watches were manufactured by J. Bidlingmaier GmbH in Schwabisch Gm/nd, Germany. In 1967, Bidlingmaier made some prototypes, the B 8 and B 9, which never came into production.

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Copyright by Pieter Doensen

email: doensen@xs4all.nl

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