This standard covers interface and performance specifications of television transmission service channels. Hypothetical reference channels have been defined and utilized to apportion performance parameters. Television signals created or transmitted in accordance with other standards or make-ups may not necessarily be compatible with the specifications of this standard. This standard specifies the performance of transmission service channels provided to convey 525-line@ System M-National Television Systems Committee (NTSC) color or monochrome video signals and their associated audio signals only. This specification for television transmission service channels applies to both interface and performance parameters. The performance parameters are expressed as a function of the length between the endpoints of a channel or as a function of the facility type utilized. Performance definitions and measurement methods are provided if appropriate. Interface specifications are provided to facilitate compatibility between end users@ service providers@ and carriers. The performance characteristics identified within this standard apply to the transmission quality between the defined interfaces. Those interfaces are: (1) between transmission service providers and end users; and (2) between the jurisdictions of one transmission service provider and another. This standard defines neither the interconnection nor the performance characteristics of specific apparatus or equipment. Purpose The purpose of this standard is to assure the uniform application of standard values of transmission parameters for television signals transported by portions of the telecommunications network. It is intended to provide a common understanding by both suppliers and their customers. Application The primary applications of this standard are for specifying and evaluating the performance of a transmission service provided by common carriers. These services are used to transport the audio and video portions of broadcast-quality television signals.