I'm playing around with an oscilloscope and my laptop's headphone jack. I get the tip/ring/ground and measure between them. I also measure between them and an external reference ground. I notice I can see when the battery is charging. That is, if the battery is not in the laptop but the AC is in, then I insert the battery, it runs through some software or something in the battery for a few seconds and then if the battery is not full, it goes to a waveform - if it is full, it goes to another "quieter" waveform. I am just doing this for fun. Can anyone think of interesting experiments I can do? I would like to see about extracting signal from the noise of the waveform. Thanks!!!