The flight-proven CTR-S is a compact, low-cost, and low-power component for full duplex digital data transmission in spacecraft. It uses differential and convolutive encoding with QPSK modulation for telemetry and PCM, PM, and SP-L modulation for telecommand, ensuring reliable, high-performance Telecommand (TC) and Telemetry (TM) for spacecraft missions using Commercial Off-the-Shelf (COTS), ITAR-free components.