INT 14h,  10h    Extended Control-C / Control-K checking and transmit on/off

            Parameters:
      Entry:  AL         Bit mask (see below)

              DX         Port number

      Exit:   AX         0001h - Control-C/K has been received
                         0000h - Control-C/K has not been received

    This is used for BBS  operation,  primarily.  A bit mask is passed in AL
    with the following flags:

                Bit 0   Enable/disable Control-C / Control-K checking
                Bit 1   Disable/enable the transmitter

    The Enable (bit 0 = 1) and Disable (Bit 0 = 0) Control-C/Control-K check
    function is meant primarily for BBS use. When the checking is enabled, a
    Control-C or Control-K received  from the communications port will set a
    flag internal to the FOSSIL driver,  but will not be stored in the input
    buffer. The next use of this function will return the value of this flag
    in register AX then clear the flag for the next occurrence. The returned
    value is used by the BBS  software to determine whether output should be
    halted or not.

    The Disable (Bit 1 = 1) and Enable (Bit 1 = 0) Transmitter function lets
    the application restrain the asynchronous driver from output in much the
    same way as XON/XOFF would.