Command Data Telemetry Simulators offer a dynamic way to create or change a PCM data stream on a word by word basis on the fly. This PCM data stream can be used to modulate an FM or SOQPSK RF output at S-Band or L-Band. In addition to simulating a new telemetry stream, the telemetry simulators can play back and loop an archived data file (which can also be changed on the fly) or create pseudo-random patterns.