one ring then disconnect.  CID said "Local Number" (portland, OR)

one ring, no message, said Local Number

Answered the call.  A few seconds of silence, then a hang-up.

one ring and dead. Quit calling.

Same thing--one ring and then nobody home.  I picked it up when they called my second line.  Some boiler-room political campaign with a pro-choice agenda.  Apparently a robo-dialer that just hangs up if there's no one available to give you their spiel.