The TCR subsystem is comprised of all the equipment needed to transmit data from the satellite to the ground in the form of telemetry.  It is the interface to receive commands from the ground and provides paths to rough ranging signals received from the ground back down to the ground for range measurements used in orbit determination.  Ranging signals received have to be converted from the receive frequency to the transmit frequency and then transmit back to the ground.  Some of the units employed by this subsystem are transmit and receive antennas, command receivers, telemetry transmitters and range signal translators.