This standard is applicable to the interconnection of data terminal equipment (DTE) and data communication equipment (DCE) employing serial binary data interchange. It defines: Section 2 - Electrical Signal characteristics:- Electrical characteristics of the interchange signals and associated circuitry. Section 3 - Interface Mechanical Characteristics:- Definition of the mechanical characteristics of the interface between the data terminal equipment and data communication equipment. 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 data terminal equipment and data communication equipment. Section 5- Standard Interface 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 Section 7- Glossary of New Terms. This standard includes thirteen specific interface configurations intended to meet the needs of fifteen defined system applications. These configurations are identified by type, using alphabetic characters A through M. In addition, type Z has been reserved for applications not covered by types A through M, and where the configuration of interchange circuits is to specified, in each case, by the supplier. This standard is applicable for use at data signaling rates in the range from zero to a nominal upper limit of 20,000 bits per second. This standard is applicable for the interchange of data, timing and control signals when use din conjunction with electronic equipment, each of which has a single common return (signal ground), that can be interconnected at the interface point. It does not apply where electrical isolation between equipment of opposite sides of the interface points is required.