"At the second tier is the Ranger. Rangers are larger robots used to transport, deploy, and coordinate the Scouts. Scouts are wholly original robots with cylindrical bodies 40 millimeters in diameter and 110 millimeters in length. The Scout carries a sensor payload used to relay environmental information to other robots. The most common Scout payload is a small video camera, but other payloads, such as microphones, are also used. Video data is broadcast to other systems via an analog RF transmitter. Scouts communicate with other robots using an RF data link..."

See the whole transcript at Introduction to robotics - Lecture 11