The Speech Security Equipment (VINSON), TSEC/KY-57, is a portable, tactical cryptographic device in the VINSON family, designed to provide voice encryption for a range of military communication devices such as radio or telephone.
The KY-57 can accept signal fades of up to 12 seconds without losing synchronization with the transmitting station. There are storage positions for 6 keys. Keys 1 to 5 are traffic encryption keys (TEK). Key 6 is a key encryption key (KEK) used for over the air rekeying (OTAR) of the other 5 keys. Key 6 must be loaded manually using a fill device such as the AN/CYZ-10.