KG-40A MT-4416/A Serial Mount The KG-40/40A is a half-duplex digital device used to provide cryptographic security protection for the Navy Link 11 system and any data communications meeting Tactical Data Information Link (TADIL) A data standards. It links the computer and the data terminal set. The KG-40A serial configuration (KG-40A-S) is used in the Airborne Tactical Data System (ATDS) and the parallel configuration (KG-40A-P) is used in the Navy Tactical Data System (NTDS).