CTTY devicename
     Specifies that a remote terminal will be used instead of the primary
keyboard and screen. CTTY is used to connect a terminal to a communications
port so that it can be used as a secondary terminal.
    OPTIONS
          devicename     Specifies AUX, COM1, COM2, COM3, or COM4
                         to be used as the primary console.
    VERSION
          PC-DOS 2.0+
	  MS-DOS equivalent: CTTY (2.0+)
    TYPE
          Internal
    EXAMPLE
	  CTTY COM1
	  redirects input and output to the COM1 port.
    MESSAGE
	  Invalid device
DOS does not recognize the device name you specified. Reissue the 
command, using a valid device name.
    UNDO
     After you have switched the console to another port, you 
must use the new console to switch back to the regular console by 
giving the command
	  CTTY CON
If the new terminal is not set at the correct baud rate and 
protocol, you may have to reboot to use the regular terminal 
again. 
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		  [For related topics, press R]
    SEE ALSO
          BREAK Command
          COMMAND Command
          EXE2BIN Command
          JOIN Command
          KEYB Command
	  KEYBxx Command
          PROMPT Command
          SET Command
          SUBST Command
 - Ref PC Magazine Vol 6, No 12, Page 497
 PC As we've discussed previously, do not use CTTY NUL to hide the output of
 TSR (terminate-and-stay-resident) programs. Due to a quirk in tDOS, each TSR
 program you load that way will permanently tie up two file handles, making
 them unavailable to your other programs. Redirecting the output of a TSR to
 NUL produces the same problem, though it ties up only one file handle each
 time. If you have an EGA or VGA system it's much smarter to simply set every
 palette color to black, as shown above.