Since the first person to descend must measure the length of the rope and must finish at the water’s edge, the other person holds the figure 8 loose without the key so I can give him slack.

The person going down uses a whistle to indicate how much slack he needs to give, then begins to descend. When he sees that there isn’t enough rope, he whistles twice. These are the syllables of CA-LA. At this point, the person descending stops, and I begin lowering him with the figure 8.

When he realizes that there is enough rope, he whistles to tell me the word STOP, and then I go and tie the key. There are two more communications: LI-BE-RA (three whistles), and REC-CU-PE-RA, which are four whistles.