Dec 142017
How to use the CTTY DOS command to control a remote PC via modem.
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How to use the CTTY DOS command to control a remote PC via modem.
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The CTTY Command of DOS 2.0

Carl H. Pelto
South East Michigan Computer Club

There are two ways to use the CTTY
command to drive an IBM PC with a
remote terminal.

1. Direct Connection

When computers and terminals are
configured as DTE (data terminal
equipment), the send and receive
lines have to be swapped. Another
way is to use a null modem
adapter at the serial cable
connection. With this connection
made, type:

MODE COM1:300,,,,

To verify that the serial port is
active and wired correctly to the
other terminal, type:


This redirects the standard
output of the DIR command to the
initialized COM1 port to test the
signal path. If the remote device
sees the DIR results, you're all
set. Then type:


Now run any DOS command from the
remote terminal. When finished,
type from the remote terminal:


This restores control to the host
IBM computer.

2. Modem Connection

To use a smart modem with this
command, develop two batch files
to initialize the serial port and
set the modem to auto answer. To
create the first file, type:


F6 puts an end-of-file mark,
control Z, at the end of the
file. To create the second file,

MODE COM1:300,,,,

To set up for an incoming call,
simply type:


You will see the running of the
batch file and its messages up
until the CTTY COM1 command.
Every thing will then freeze up
until the phone rings, the modem
answers and sends the DOS prompt
A> to the remote terminal. As
with the direct connection, the
remote can run most DOS commands,
including ERASE *.* and FORMAT,
so be careful. To return control
to the host IBM PC again, type
CTTY CON from the remote. I hope
you have as much fun with this
command as I have had.

0N81N Washington Conne

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