MIL-STD-2179B, MILITARY STANDARD: HELICAL DIGITAL RECORDING FORMAT FOR 19-MM MAGNETIC TAPE CASSETTE RECORDER/REPRODUCERS (14 DEC 1990) [NO S/S DOCUMENT]., The purpose of this standard is to ensure the ability to exchange digital data within the appropriated community of users in the Department of Defense, to standardize the cassettes and the format of the data for 19-mm magnetic tape and to ensure that a recording made on one machine can be replayed on any other machine that conforms to this standard.