One of the more useful packages I found was called sound card oscilloscope, which is available for download from http://www.zeitnitz.de/Christian/scope. The following screenshot was taken from this package when it was in use. The only downside of this package is that it does not use the full 96 KHz sample rate of the sound card I am using.

Signal generator window

The preceding screenshot shows the signal generator window, which is detachable from the main scope window—a handy feature in my opinion.

An oscilloscope

The preceding image shows the resulting output from our black box. Unfortunately, we only have a 48 KHz sample rate, so the highest frequency we can generate is about 24 KHz. Also, the software can only use 16 of the 24 bits, so the sine wave is not as clean as it would have been if we had been able to use all 24 bits.

You will recall that the interface has a times-ten and a times-one probe selector switch. The following screenshots are of the main oscilloscope...