{{isoimg|FDTD66.png|[[FDTD Module]]'s output window.}}
===Waveforms Excitation Waveform & Discrete Fourier TransformsFrequency Domain Computations ===
When an FDTD simulation starts, your project's source starts pumping energy into the computational domain at t > 0. Maxwell's equations are solved in all cells at every time step until the solution converges, or the maximum number of time steps is reached. A physical source has a zero value at t = 0, but it rises from zero at t > 0 according to a specified waveform. [[EM.Tempo]] currently offers four types of temporal waveform: