Source : Free On-Line Dictionary of Computing

high speed serial interface
     
         (HSSI) A {serial port} which
        supports serial transmit speeds of up to 52 megabits per
        second.  It is typically used for leased lines such as {DS3}
        (44.736 Mbps) and {E3} (34 Mbps) and for {Wide Area Network}
        devices such as {routers}.
     
        (1995-11-20)