FASTLANE, designated TSEC/KG-75, is a family of bulk encryption of packet stream devices specified by the National Security Agency and manufactured by General Dynamics. The device interfaces to Asynchronous Transfer Mode (ATM), Synchronous Optical Network (SONET), and Synchronous Digital Hierarchy (SDH) interfaces, at speeds from 155 Mbps (OC-3) to slightly under 10 Gbps (OC-192).  It encrypts packets within frames, and certainly not all bits; the frame headers and trailers must be present for the LAN to work.
It is the parent of the newer TACLANE TSEC/KG-175 for packets over LAN, and replaced the TSEC/KG-189 for SONET and SDH.
FASTLANE is the main interface for classified traffic flowing directly onto circuits on the Defense Information Systems Network; it encrypts Asynchronous Transfer Mode (ATM) information and sends it to an ATM switch.
- FASTLANE® ATM/SONET Encryptor (KG-75/KG-75A), General Dynamics C4 Systems