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A protective distribution system (PDS), also called ''protected distribution system'', is a US government term for wireline or fiber-optics telecommunication system that includes terminals and adequate acoustical, electrical, electromagnetic, and physical safeguards to permit its use for the unencrypted transmission of classified information. At one time these systems were called "approved circuits". A complete protected distribution system includes the subscriber and terminal equipment and the interconnecting lines. ==Description== The purpose of a PDS is to deter, detect and/or make difficult physical access to the communication lines carrying national security information. A specification called the National Security Telecommunications and Information Systems Security Instruction (NSTISSI) 7003 was issued in December 1996 by the Committee on National Security Systems. Approval authority, standards, and guidance for the design, installation, and maintenance for PDS are provided by NSTISSI 7003 to U.S. government departments and agencies and their contractors and vendors. This instruction describes the requirements for all PDS installations within the U.S. and for low and medium threat locations outside the U.S. PDS is commonly used to protect SIPRNet and JWICS networks. The document superseded one numbered NASCI 4009 on Protected Distribution Systems, dated December 30, 1981, and part of a document called NACSEM 5203, that covered guidelines for facility design, using the designations "red" and "black".〔 There are two types of PDS: hardened distribution systems and simple distribution systems. distribution fast as compare to transmission systems due to more load consuming. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Protective distribution system」の詳細全文を読む スポンサード リンク
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