Find air-taser
After you have gotten the transponder, head to the towering rocks to use it, stop right before you get there. You will notice 2 guys talking and kinda guarding where you need to use your transpoder. This is where you will find a strange small square rock. (About the size of Gabe, your character. Climb on to of the rock. Now turn around drop down and grab the OTHER side. You will see a platform. On it will be an air-taser.