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Estyma Mantel Clock (early transistor)
(Impulsed; moving magnet; electronically switched)


Estyma

This mantel clock is one of the earliest designs to use a transistor to switch the current to an impulse coil. The clock has a slightly tapered glass dome to protect it from dust and give maximum viewing of the pendulum.

The pendulum has a bob in the form of a curved magnet, both ends of which swing through separate coil assemblies. The coil on the left is the 'trigger' coil and the coil on the right is the 'impulse' coil. As the pendulum swings to the right, the magnet on the pendulum induces a current in the trigger coil which switches the transistor on. This passes an impulse current through the right hand coil, and attracts the right end of the magnet on the pendulum. As the pendulum then swings to the left, an opposite polarity current is induced in the trigger coil which switches the transistor off, and thus switches the impulse current off.



The pendulum drives the hands through a crutch and an indexing pawl which advances a wheel one tooth each complete swing.
Estyma
Estyma

The battery and electronics are contained in the plastic base of the clock and, by today's standards, are relatively crudely constructed  using a tag strip, not a printed circuit board.


Detail of the electronics.
Estyma
Voltage: 1.5v
Battery type: one LR14/MN1400/C size cell
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Copyright  Text & Pictures - Martin Ridout.   Last updated Jan 2005.