Study this SIGNAL exclusively.
Only this one.
Money Heist Season 3, Episode 5
When Mance gives the SIGNAL
and we hit Castle Black,
Game of Thrones Season 3, Episode 7
to give you the SIGNAL
to light the trench.
Game of Thrones Season 8, Episode 2
...this will register it
and send a SIGNAL to the laptop.
The Big Bang Theory Season 1, Episode 11
How will we see your SIGNAL?
Game of Thrones Season 3, Episode 3