The crystal oscillator is an integral component for clock creation in digital data transmission circuitry. There tends to be two primary job functions of a crystal oscillator in electronic circuits. The first purpose is to drive the circuit independent of the environment. This is typically the purpose in standard consumer electronics. In this situation, drift and the accuracy of the crystal is not critical as the crystal oscillator is the only reference for all the components within the circuit. The second purpose is to synchronize the oscillator output with an incoming signal, which often requires a voltage controlled crystal oscillator.