This standard is applicable to the interconnection of data terminal equipment (DTE) and data circuit-terminating equipment (DCE) employing serial binary data interchange. It defines: Section 2 Signai Characteristics: Electrical and grounding characteristics of the interchange signals and associated circuitry. Section 3 Interface Mechanical Characteristics: Definition of the mechanical characteristics of the interface between the DTE and the DCE. Section 4 Functional Description of Interchange Circuits: Functional description of a set of data, timing and control interchange circuits for use at a digital interface between a DTE and a DCE. Section 5 Standard Interfaces for Selected Communication System Configurations: Standard subsets of specific interchange circuits are defined for a specific group of data communication system applications. In addition, the standard includes: Section 6 Recommendations and Explanatory Notes