Silence when you pick up the phone always indicates a robocall is in progress.  Sometimes they never answer, rolling to the first call to pick up and dropping the rest.  Other robocall machines listen for a live person.  After a few encouraging "Hello telemarketer . . . " and "Come on robo-call, you can connect . . . ," from me it did.  The telemarketer said he was from the Colorado Police Association or something like that.

Police, Sheriff, and other law enforcement entities used to make calls themselves to raise money for good causes.  People gave because they figured doing so was "insurance" against "imperial entanglements," or that the failure to give would surely result in police harassment, extra speeding tickets, etc.  None of which is true, of course.

The police haven't been making their own calls in decades.  Realizing the intimidation factor that comes with announcing to some hapless caller (on Mothers' Day, no less) "this is the police!," paid solicitors have been running this racket since the 1970s, remitting some to the police (assuming its not a complete scam), but keeping a huge percentage for themselves.  A curt, "Yeah, [***], goodbye" from me is all this jackwad received.