====== Power source ======
The drive provides the clock or [[watch]] with the energy it needs to function. ([[Elementary clock]]s work differently and are described separately.) For **mechanical watches** weights or springs may be used as drive unit and for **electrical watches** magnetic fields (magnetic coil motor).

===== Weight drive =====
Weight drive is the simplest form of the drive for clock movements. The major advantage of weight train is that the driving force is constant.

A **chain hoist** depends on the weight on a chain that via a sprocket drives the [[movement]]. The running back the chain after winding is prevented by a [[ratchet]]. Chain hoists are, inter alia, used in longcase clocks, [[black forest clock]]s and cuckoo clocks.

With a **wire rope hoist** the weight hangs on a rope or on a pulley. Through the pulley, the height of the weight is halved. When winding the rope is wound on a pulley with a keywind-up. The running back of the rope after winding is prevented by a ratchet. Wire rope hoist is, inter alia, used in wall clocks, longcase clocks and church clocks.

In order to supply the [[movement]] with power also during winding, better clocks with weight drive have a counter ratchet.

===== Spring drive =====
The drive of the [[movement]] is supported by a taut steel tape, coiled in a spiral the [[mainspring]]. In general, the spring is housed in the [[barrel]]. The outer end is hooked on the [[barrel]]. The inner end is attached to the axle, the spring core.

When winding (tensioning the spring), the spring is wound around the spring core. There are fixed, movable and flying barrels. The relaxation of the spring after winding is prevented by a [[ratchet]].

The spring drive is used since the 16th century.

Since the spring force changes within wide limits during the expiration, the fixation or the [[snail]] were used to provide a uniform power delivery to the wheels. With improvement of spring materials these facilities could be dispensed over time.

===== Magnetic field (electric drive) =====
Electric watches have direct or indirect electric drive and derive their operating power from line voltage, battery, solar cells or the [[autoquartz]] system by converting kinetic energy into electrical energy (dynamo principle).

With **direct electric drive**, as it is used with the common [[quartz]] [[wristwatch]]es,

  * a motor (synchronous motor or stepper motor) or
  * a magnetic coil using a [[pendulum]], a [[balance wheel]] or a resonator ([[tuning fork]])

drives the [[gear train]].

With **indirect electric drive**, the mechanical energy storage ([[mainspring]]) is charged by folding-anchor or motor.


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