The KYV-5 is part of the Advanced Narrowband Digital Voice Terminal (ANDVT) family.

These terminals are handled as UNCLASSIFIED controlled cryptographic items (CCIs) when unkeyed; when keyed they assume the classification of the key. The ANDVT family provides joint interoperability between Service components of US command elements and North Atlantic Treaty Organization allies.

ANDVT Family units are primarily used to satisfy tactical secure voice requirements on high frequency (HF), very high frequency (VHF), and ultra high frequency (UHF) satellite and line-of-sight (LOS) communications; UHF Non-Demand Assigned Multiple Access (Non-DAMA) and DAMA; super high frequency (SHF) and extremely high frequency (EHF) satellite communications (SATCOM) including Milstar; UHF Follow-on (UFO)/EHF; and Fleet Satellite EHF Package (FEP). All ANDVTs must have engineering change proposal-060 (ECP-060)/field change -1 (FC-1) incorporated in order to operate over UHF SATCOM.

The KYV-5 is a small unit that attaches to the front of the larger CV-3591 converter. That's real easy to see in the 3/4 photo below.

The TACTERM normal configuration consists of the Basic Terminal Unit (BTU) (the large grey CV-3591) and a communications security module (KYV-5), providing half-duplex, secure transmission of voice or data communications in either point-to-point or netted mode