This is rare - the 2nd call from this particular number. It's from my cell phone prefix and I've noticed lots of similar calls recently.  Until now, no repeat calls and never any reports on 800notes.  I believe the spammers choose an area code and prefix for their caller ID (in this case 951-970-xxxx) and have their robot systematically call all 10,000 numbers that are possible for that prefix: 951-970-0000, 0001, 0002, 0003, etc.  If the computer calls 100 numbers at a time, it wouldn't take long to call all of them - probably less than an hour.  Of course, it looks like a familiar number to me so I might be more inclined to answer.