In general, there is an electronic 'gearing mechanism' of some form; for example, a digital clock has a component called a 'counter' to handle gear. There also a display, which is usually either LEDs(light- emitting diodes) or an LCD(liquid crystal display).In a digital clock, this is usually given by a glass crystal.When an electric charge passes through the crystal, it changes shape and emits a very mild sound.The sound, which is heard at a regular frequency, is then translated into an electronic signal.To keep time, digital clocks typically use an AC oscillator of 50 or 60 Hz or a 32, 768 - hertz crystal oscillator like a quartz clock.The quartz crystal oscillator vibrates swiftly and precisely(32, 768 times / second) in response to the electrical charge.The circuit keeps track of the vibrations and sends out one - second electric pulses.The pulses drive a small electric motor, which spins the watch hands and keeps accurate time.