As Alan Grant, Ellie Sattler, and Donald Gennaro were about to descend into the Velociraptor nest, they needed to inspect what was inside before entering. Alan Grant tied a small handheld video camera with an attached monitor to a rope, and then lowered it down the narrow entrance so that he could see. The visibility in the nest was poor, and so Grant utilized the microphone feature to determine how many animals were in the nest. After determining the number of animals in the nest, Grant pulled the camera up and set it on the ground, abandoning it as they went into the nest.
Jurassic Park by Michael Crichton page 378 (First Edition, Thirty Fourth printing)