They called once and I spoke to a man with an accent that said he was taking a survey and proceeded to verify my name and address, then asked if I had an alarm system installed in my home. I was very suspicious at his point and did not answer.
Just received another call from this same number that came up "Alarm Systems" but I let my answering machine pick up.  I heard deep breathing and low voices as though this person was in a room full of people making the same phone calls, they hung up without leaving a message.