Electric Clock - Types

Types

Electric clocks can operate by several different types of mechanism:

• Electromechanical clocks These have a traditional mechanical movement, which keeps time with an oscillating pendulum or balance wheel powered through a gear train by a mainspring, but use electricity to rewind the mainspring with an electric motor or electromagnet. This mechanism is found mostly in antique clocks.
• Electric remontoire clocks In these, the gear train was turned by a small spring or weighted lever, called a remontoire, which was wound up more frequently by an electric motor or electromagnet. This mechanism was more accurate than a mainspring, because the frequent winding averaged out variations in the clock's rate caused by the varying force of the spring as it unwound. It was used in precision pendulum clocks, and in automotive clocks until the 1970s.
• Electromagnetic clocks keep time with a pendulum or balance wheel, but the pulses to keep it going are not provided by a mechanical movement and escapement linkage, but by magnetic force from an electromagnet (solenoid). This was the mechanism used in the first electric clocks, and is found in antique electric pendulum clocks. It is also found in a few modern decorative mantel and desk clocks.
• Synchronous clocks rely on the 50 or 60 Hz utility frequency of the AC electric power grid as a timing source, by driving the clock gears with a synchronous motor. This type of clock was widely used from the 1930s to the present.
• Quartz clocks are electric clocks which keep time with a vibrating quartz crystal. They are the most common type of clock today.