Input tax credit availability on ducts and manholes upheld; ITC not blocked for OFC network infrastructure. Input tax credit on ducts and manholes used in optical fiber cable networks is not barred under the exclusions in section 17(5) because such ducts and manholes fall within the Explanation's concept of 'plant and machinery' used for making outward supply of telecommunication services and are not excluded as land, buildings, civil structures, telecommunication towers or pipelines laid outside factory premises.