Model C/TT-505 UHF Command Telemetry Transceiver is designed to provide a wireless RF link between two orbiting spacecraft or other crafts such as a Lander on the surface of Mars, and an Orbiter craft orbiting above. The purpose of these transceivers is to facilitate the passing of data and commands between the two craft. One UHF transceiver is required for each vehicle i.e., one for the Lander and another for the Orbiter.