9 - 15 (2) Air Traffic Controller. The ATC (air traffic controller) is a locking mechanical belay device (Figure 9-18). It locks down on itself once tension is applied in opposite directions. This requires the belayer to apply very little force with his brake hand to control the rate of descent or to arrest a climber’s fall. Figure 9 -8. AIR TRAFFIC CONTROLLER 9-9. CLIMBING COMMANDS. Table 9-1 shows the sequence of commands used by climber and belayer. Table 9-1. SEQUENCE OF CLIMBING COMMANDS Command Given By Meaning BELAY ON, CLIMB Belayer Belay is on and climber may climb. CLIMBING Climber Climber is climbing. UP-ROPE Climber Belayer, remove excess slack in the rope BRAKE Climber Belayer, immediately apply brake. FALLING Climber Climber is falling, immediately apply brake, prepare to arrest the fall. TENSION Climber Belayer, removes all slack from climbing rope until rope is tight, apply brake, hold position. SLACK Climber Belayer, allows climber to pull slack into the climbing rope (belayer may have to assist). ROCK Anyone Command given to alert everyone of an object falling near them. Belayer immediately applies brake. POINT Climber Alert belayer that the direction of pull on the climbing rope has changed in the event of a fall. STAND-BY Climber or Belayer Hold position, stand by, I am not ready. DO YOU HAVE ME? Climber Informal command to belayer to prepare for a fall or prepare to lower me. I HAVE YOU Belay The brake is on and I am prepared for you to fall, or to lower you. OFF-BELAY Climber Alert belayer that claimer is safetied in or it is safe to come off belay. 3-METERS Belayer Alert climber to the amount of rope between climber and belayer (May be given in feet or meters) BELAY-OFF Belayer I am off belay 9-10. ROPE INSTALLATIONS. Rope installations may be constructed by teams to help units negotiate natural and man-made obstacles. Installation teams consist of a squad-sized element with 2 to 4 trained mountaineers. Installation teams deploy early and prepare the AO for safe, rapid movement by constructing various types of mountaineering installations. Following construction of an installation, the squad, or part of it, remains on site to secure and monitor the system, assist with the control of forces across it, and adjust or repair it during use. After the unit passes, the installation team may disassemble the system and deploy to another area.