If you have a Java enabled browser, the FFT-Lab applet will appear below. Getting started: Click and drag with the mouse in the lollipop display to draw or change the curves. Select what effect clicking and dragging has on the graph from the "Editing" menu below. This applet is based on free Java source code originally developed by Dave Hale (c)1996 and extended by Stephan Bernsee (c) 2004. [Download offline version (15kB, ZIP)]   Version history Version 2.0 Initial release of the improved version Version 2.01 Fixed a bug causing "negate" to negate magnitude as well. Magnitude is always positive, a sign change would cause the phase to change. Version 2.02 Fixed a bug causing redraw problems in IE5 on the Mac. Auto-scaling now works consistently across all domains. Added "Constant" and "Rectify" options in the Editing menu.