I don't believe this is possible on the XM. As an alternative I run a low frequency program such as abdominal cramps, with a ramp up of 20 seconds. I connect my TENS pads, and then run the program, with my finger on the STOP button. I can usually feel it around 10volts and then hit stop. Once I've run my test I load up my real treatment program.
I've had a broken TENS cable before, so I religiously do my test every time I run contact. To save time I saved the above as a preset.
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