We have four types of signal generators, which having some differences among them. Function generators is the most widely used signal generator to provide sine wave, saw tooth wave, square wave, pulse wave and other waveforms, and some also have modulation and scanning function. Arbitrary waveform generators is a kind of special signal source, which not only has the ability of general signal source waveform generation, but also can simulate the actual circuit test of arbitrary waveform. Pulse/pattern generators can generate a rectangular pulse with adjustable width, amplitude and repetition frequency. Synthesized signal generator signal not by the oscillator, but with high stability quartz oscillator as the standard frequency source, form for arbitrary frequency signal using frequency synthesis technology, with standard frequency source with the same frequency accuracy and stability.