TADIL-J refers to "Tactical Digital Information Link Joint" (TADIL) which was used by the U.S. Navy, U.S. Army, U.S. Marine Corps, U.S. Air Force, the NSA, several NATO countries, and Japan as part of the Multi-Tactical Data Link Network (MTN). TADIL-J refers to the system of specialized data radios and specially-formatted messages ("J" series messages) which is the predecessor to the Link 16 system defined by military standard, MIL-STD-6016D.
Other TADILs included TADIL-A, TADIL-B, and TADIL-C whose designations were replaced by Link 11, Link 11B, and Link 4 respectively.
TADIL is no longer an official US Department of Defense term (per DISA guidance). Instead it has officially been replaced by the generic term Tactical Data Link (TDL). However, the term "TADIL" is a legacy holdover and still used in the vernacular.
Tactical Digital Information Link