The present document is an introduction to the other parts of this multi-part deliverable dealing with the speech processing functions in the TETRA system. In addition to this introduction, the present document contains the full specification of the speech CODEC including provisions for specific cases of operation and optional functionalities plus CODEC conformance testing. The present document also contains the full specification for the optional AMR CODEC as implemented within the TETRA system. In the present document, a general overview of the speech processing parts is given with reference to the multi-part deliverable where each part is specified in de