To select a function, you may press one of the following buttons: Sine, Triangle, Sawtooth, Square, and Noise. The function is displayed in white, with the Fourier series approximation in red. You can edit the function directly by clicking on it.
This applet has sound if you are using java 2. If you don't see a "Sound" checkbox, then you should get the Java plug-in.
Index of examples.
Download zip archive of this applet. (double-click on index.html to run)
Digital Filters Applet.
Version 1.6c, posted 2/1/14