Crystals are naturally occurring materials that can be induced to resonate or vibrate at an exact frequency. Quartz, a piezoelectric crystal that provides excellent mechanical and electrical stability, acquires a charge when compressed, twisted, or distorted. Typically, quartz crystals are used as active elements in oscillators. Applying mechanical stress to quartz produces a voltage that is proportional to the mechanical frequency of the vibration. Conversely, applying an AC voltage induces vibrations at the frequency of the applied voltage. These mechanical vibrations provide a standard of time that is superior to that of mechanical clocks, but inferior to that of atomic vibrations. In some circuits, crystals are made from thin sheets of quartz and plated like integrated circuits (IC). Amplifying noise at the crystal’s frequency induces continuous oscillation, the periodic movement between two points. The oscillator output is then converted to pulses that are suitable for digital circuits. In turn, these pulses divide down the crystal’s frequency and translate it into a format for display.