9 November 2016, the caller did what you folks describe that it rings a portion of one ring and then hangs up. Anymore, if it is a strange phone number, I just DO NOT ANSWER the phone and then I wait to see if a message was left. Then I will call back the person if I trust that message. Otherwise, it is naive to answer those unknown calls anymore. There are too many types of ID Theft afoot these days. I just don't comprehend how any of these idiot callers make any money to pay for their robo-calling machines.
On TV, the continual advertisements for MORGAN AND MORGAN law firm tell us they can get us $1,500 per phone call. You first must make sure you are on the NATIONAL DO NOT CALL LIST and if you do talk to someone, you need to tell them "REMOVE ME FROM YOUR LIST!" The law(s) require them to stop calling you.