The unknown creeps called close to 15:00 Eastern. The CNAM was a useless place name default, "Hemet CA".
I answered at the third ring; a reasonable response time, I thought. Not good enough for this bunch. Ten seconds past the first call, they called a second time while I listened to silence and Call Waiting tones. I did not respond to the second call, since I usually ignore the feature and did not realize it was the same calling party. This "double tap" crap has been reported a few other times the past month, an apparent brute force solution to defeating whatever form of call screening you like.
The carrier is Local Access Services LLC. The number is in Los Angeles. The only other call I have in my records matching those two attributes was on 09 April 2016, reportedly a breast cancer commercial fundraiser, which is to say charity fraud. This speculation of course does not make a pattern.