This function generator supports sine,square,triangle, sawtooth and noise. Frequency range for soundcard is 20Hz to 20khz. Serial and parallel port is 1 Hz to 1KHz. Supports creating wave files. Supports command-line parameters(which on the free version has a nag screen when using parameters, buying off of eBay will remove the nag screen). It can also create a batch file with the current settings for easy use. It has a sweep that changes the frequency every interval as low as 1mSec. Command-line help screenshot is in this auction. The password you get will work on all versions including new ones in the future. You can download it, and try it yourself nothing is disabled except the nag screen when any command-line parameter is used. The link is in the auction pictures since ebay will not allow hyperlinks. Serial and parallel ports only make square waves and amplitude is not configurable on them only on soundcard. It has pinouts an also a common emitter amplifier for soundcard which enables higher voltages output. Note you will not receive an item in the mail, just the password which is used to remove the nag screen. It works on linux with Wine except the amplitude can't be changed. Password can be use on any number of computers and any number of times. Buying this app supports people with Autism Also if you use it in wine under Linux you will need to install pulseaudio-utils package(If you want VoltXP have the capability to change amplitudes)