This publication, Training Circular TC 6-02.20 Cable and Wire Systems Handbook January 2018, Cable and Wire Systems Handbook, is a reference-based handbook for personnel who install, maintain, test, troubleshoot, repair, fabricate, replace, and recover wire and cable for Army communications networks. This publication is a guide to implement unit sustainment training for military occupational specialty (MOS) 25L and Soldiers requiring knowledge of signal wire and cable installation to support the mission. Commanders, staffs, and subordinates ensure their decisions and actions comply with principles and expectations of the Army profession and any applicable United States, international, and, in some cases, host-nation laws and regulations. TC 6-02.20 contains general information on wire, cable, connectors, outside plant operations, inside plant operations, local area network (LAN) and wide area network (WAN). It covers installing and recovering wire and cable lines, pole climbing, splicing, wire ties, troubleshooting, wire line construction, and wire records. It mentions characteristics of typical communications equipment that utilize wire and cable technologies. TC 6-02.20 uses joint terms where applicable. Selected joint and Army terms and definitions appear in both the glossary and the text. Terms for which TC 6-02.20 is the proponent publication (the authority) are marked with an asterisk (*) in the glossary. The text of Definitions for which TC 6-02.20 is the proponent publication are boldfaced. For other definitions shown in the text, the term is italicized and the number of the proponent publication follows the definition. This publication applies to Active Army, the Army National Guard, and the United States Army Reserve unless otherwise stated. The proponent of this publication is the United States Army Cyber Center of Excellence.