The HSSI network interface resides on a modular port adapter, which provides a direct connection between the high-speed bus in the router or switch and the external networks. The PA-H single-port HSSI port adapter provides one high-speed serial interface.The PA-H conforms with the BABT/TC/130 and EIA/TIA-612 and EIA/TIA-613 standards for HSSI. The PA-H provides one interface, which provides a full-duplex, high-speed, synchronous serial interface for transmitting and receiving data at rates of up to 52 Mbps. The HSSI has been standardized as EIA/TIA 612/613 and provides access to services at T3 (45 Mbps), E3 (34 Mbps), and Synchronous Optical Network (SONET) STS-1 (51.82 Mbps) rates.