DoD Directive 5100.41: Executive Agent Responsibilities for the National Communications System (NCS) [open pdf - 22KB]
"In this directive the President established the National Communications System (NCS). The NCS consists of the telecommunications assets of the Federal Government organizations represented on the interagency NCS Committee of Principals and an administrative structure consisting of the Executive Agent, the Manager, and the NCS Committee of Principals. The President further directed that the Secretary of Defense serve as Executive Agent for the NCS. This directive outlines NCS responsibilities and its method of organization."
DoD Directive 5100.41; DoDD 5100.41