The designation 3270 is a manufacturer-specific designation from the IBM company for SNA peripherals that includes control units and terminals. These devices communicate with the host either via Synchronous Data Link Control( SDLC) or Binary Synchronous Communication( BSC). In the SNA architecture, the 3270 devices are referred to as Logical Units( LU). The transmission speed was 2.35 Mbit/s, and RG-62coaxial cable with 93 ohms was used as the transmission medium.
3270 terminals were connected to the 3174 cluster controllers.