Standard galactic code
From Tardis Wiki, the free Doctor Who reference
The standard galactic code of the 455th century was a form of communication the Ninth Doctor used to contact a spaceship trapped between the time vortex and real space. The code was communicated by the sonic screwdriver in bursts in a similar way to a Morse signal. The Doctor claimed on 1920 Earth that "everyone" knew the code. (PROSE: Doctor vs Doctor)
