Source : Free On-Line Dictionary of Computing

serial line
     
        Wires which connect two {serial port}s carrying serial data
        consisting of sequential bits represented by one of two
        voltages.
     
        A common electrical specification for the signals on a serial
        line is {RS-423}.
     
        {(ftp://ftp.acorn.co.uk/pub/documents/appnotes/231-245/234.ps)}.
     
        (1995-02-02)