Which system allows the exchange of classified information over communications security circuitry?

AUTOSEVOCOM is the correct choice for the system that allows the exchange of classified information over communications security circuitry. This system is specifically designed for secure communications that require the protection of sensitive information in transit.

AUTOSEVOCOM uses high-level encryption to ensure that the data being transmitted remains confidential and is not accessible to unauthorized users. It is widely relied upon in military and defense contexts where the integrity and secrecy of information are paramount.

The other systems mentioned, while related to secure communications, serve different purposes or operate in different capacities. HICOM, for example, is associated more with high-capacity communications rather than specifically handling classified information through secure circuitry. DSSCS focuses on specific data transmission services, but not necessarily on classified information as a primary function. NORATS serves a particular operational role in some instances but does not fulfill the need for a comprehensive secure exchange for classified material like AUTOSEVOCOM does.