Got a call about a half hour ago. Didn't answer and it only rang once. My Sentry call blocking device will block all robo calls by forcing the caller to press a key to continue the call. Robots can't do that so they get disconnected. Of course, it may have been a live person calling who chose not to press a key and just hung up. Either way, the call blocker did it's job!! Best $40 I ever spent!!