We had a couple 911 calls our first couple days with our uc540. What came up with was that our old phone system buttons had a different feel. With these cisco phones, if you press the button all the way down in a quick press, the nunbers never double for us. You can hold down forever and never get a duplicate. But if you press slowly or don't press the button all the way, I can get double numbers when pressing. I think that there's a point in the actuation that the button can float between on and off and that can give you double numbers (I think in the gaming community that this is called "spamming" the button). Our old system took less pressure to press the button all the way down and as soon as we told everyone to press harder we haven't had a accidental 911.
If you push a button half way down and shake it left to right you can see a good example of how to spam the button. Yeah, that isn't how a person dials, but the first few days we got double-numbers just with people making calls. We have a few spa and a few 7900 series and we had issues on both but more on the spa phones.
One specific person had the most trouble and this person doesn't have the most stable hands... She wasn't calling 911, but she just couldn't dial the right number because they'd get an unintentional double digit in the middle of their dialing. She really has to press every number deliberately to make calls--I wish I had a better solution for her because it makes here feel dumb.
