For support of a satellite that employs space ground link system (SGLS) communications, the real-time subsystem consists of a control central processing unit (CPU), IF receiver and subcarrier demodulator, telemetry bit synchronizer (with Viterbi decoder), pulse code modulation (PCM) decommutator and PCM simulator, Inter-range Instrumentation Group time code generator/reader and high performance small computer standard interface controller with real-time archival disk.
For example, the decommutator board uses the standard VME and VMEbus subsystem bus (VSB) interfaces for the movement of information.
These systems typically consist of a single card slot bit-synchronizer and decommutator. The bit-synchronizer recovers the clock and data from the baseband signal provided by the receiver.
Personal computer-based bit-synchronizers and decommutators are available from several sources.