The DS3251 (single), DS3252 (dual), DS3253 (triple), and DS3254 (quad) line interface units (LIUs) perform the functions necessary for interfacing at the physical layer to DS3, E3, or STS-1 lines. Each LIU has independent receive and transmit paths and a built-in jitter attenuator. An on-chip clock adapter generates all line-rate clocks from a single input clock. Control interface options include 8-bit parallel, SPI, and hardware mode. Applications * Access Concentrators * ATM and Frame Relay Equipment * CSUs/DSUs * Digital Cross-Connects * DSLAMs * PBXs * Routers/Switches * SONET/SDH and PDH Multiplexers