"The idea is that the narrator is in an altered state, and his phone starts talking to him," says the Edge.
U2 Break Down 'No Line on the Horizon', Brian Hiatt, Rolling Stone, Jan 22, 2009
Chris Taguchi christaguchi.ca (4th of March 2009)
The first notes are 7 tones repeated (3 then 4) like (speed)dialing a phone. Bono is singing as a character who is lost in life with no spiritual meaning. The time 3:33 is significant - we know Jeremiah 33:3 "'Call to Me, and I will answer you, and show you great and mighty things, which you do not know" is a favorite verse of Bono's (see the cover of ATYCLB - J33:3) and fits perfect with this song. This character doesn't realize he is stuck "on the edge of the known universe where I wantedd to be", and thinks he is where he belongs. Edge sings as God: "force quit and move to trash" is how you stop a program that is not working on a Mac. God is intervening and forcing him to start over his life and be reborn - "restart and re-boot yourself." "Hear me - don't move or say a thing" is a take on Psalm 46:10 - "Be still and know that I am God." Finally God speaks to him through music for the final 2 minutes of the song beginning with organ and French horn and then Edge's solo.
Eric Leveton levetongmail.com (27th of March 2009)
On the 2nd of July, 2009, in Barcelona, during the present 360¡ Tour, Bono told the following to the audience concerning the song U2 were going to perform next: It's about a guy at the end of his route, very dark, very depressed. He checks into a hotel room, don't know what's going to happen. He takes out his phone, can't get an outside line, no signal. Then a strange thing happens; the phone starts to text him, instructions, it gets him out of there alive. He doesn't know where it's coming from; God? Best mate? Who knows? It's called Unknown Caller.
Tom Luthander tom_luthanderhotmail.com (14th of July 2009)