Section 23.2 - Definitions(a)Adequate means appropriate and sufficient, as determined by mutual agreement of the manufacturer, operators, and MSHA.(b)Approval means official notification by letter, from MSHA to a responsible organization, stating that the device under consideration has been judged to meet the requirements of this part.(c)Normal operation means the performance by each part of the device of those functions for which the part was designed.(d)Permissible as used in this part means completely assembled and conforming in every respect with the design formally approved by MSHA under this part. (Approvals under this part are given only to equipment for use in gassy and dusty mines.)(e)Protected means effectively covered, enclosed, or otherwise guarded by adequate covers.(f)Signaling device. As used in this part, a signaling device is one that gives visual or audible signals.(g)MESA means the United States Department of the Interior, Mining Enforcement and Safety Administration. Predecessor organization to MSHA, prior to March 9, 1978.(h)MSHA means the U.S. Department of Labor, Mine Safety and Health Administration.Sched. 9B, 4 FR 1555, Apr. 11, 1939, as amended by Supp. 1, 20 FR 2975, May 4, 1955; 39 FR 24001, June 28, 1974; 43 FR 12315, Mar. 24, 1978; 47 FR 11370, Mar. 16, 1982 Paragraph (f) of this section is issued under the authority of Sec. 101 of the Federal Mine Safety and Health Act of 1977, Pub. L. 91-173 as amended by Pub. L. 95-164 , 91 Stat. 1291 (30 U.S.C. 811 ). All other paragraphs in this section continue under the original authority.