The clock is made of a case to hold the motor, the motor, a time-set knob, alarm lever, alarm mechanism, gear assembly, dial light, face, hands, some type of covering, and the power cord. An electric clock works because the motor turns gears, which in turn, move the clock hands. Some clocks have metal gears, while others have plastic. Plastic gears tend to be quieter, and are used by most modern manufacturers. Digital clocks rely on electronic circuitry, instead of gears.
Electricity powers an electronic control panel, which posts the time.
While they work well, they are difficult to fix. If you have problems with your digital clock, you will likely have to replace it. Digital clocks also must be set, and will need to be reset with a break in power. Electric clocks will stop without power, but will continue time, when power is restored. If you have returned home, and the power has been out, this is why some of your clocks might be flashing, while others are off, but still going.