1 Turn of Tuning for ESP?

The ESP spells says, in part:

"The caster must designate a direction, and then concentrate for a turn in order to “hear” the thoughts."

Now, does that mean that ESP takes 10 minutes of “tuning” (or whatever) before it starts to work, or is it simply restating the fact that “listening” with the spell requires concentration, and that you can only change the direction listened every 10 minutes?

Ludanto, it takes 10 minutes of "tuning" to work.