# Null modem



## CWEISER (Jul 5, 2000)

Have two 486 PCs running Win 3.1 with 14.4 modems. 
How can I rig a "Null Modem" to transfer files from the hardrive of the one to the hardrive of the other.


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## rogers55 (Mar 25, 2000)

CWeiser,
This quote from a M/S document describes null modem. It can be used to transfer data between computers with a program like LapLink. You can also use a parallel connection, it will be faster.

PSS ID Number: Q60040
Article last modified on 10-11-1999
WINDOWS
=============================================*********************************************This article contains general purpose information about serial communication between computers. For specific information,
contact your hardware vendor.
*********************************************
SUMMARY
=======

If two computers are within a short distance of each other, it is possible to use either a null modem cable or null modem adapter to connect the computers for serial communication.

The null modem cable for IBM computers and compatibles changes the connection of pins so that pin numbers are not connected directly to the corresponding pin numbers at the other end of the cable. In other words, pin number 2 is not connected to pin number 2.

If the lines were straight through, a transmitter pin would be attempting to talk
with another transmitter pin. A transmitter pin must be connected to a receiver pin for the transmitter to be "heard."

MORE INFORMATION
================

The alternative to the null modem cable is the use of a null modem adapter that
changes the connection between pins and allows the use of straight through
cables. A null modem adapter is also called a modem eliminator. It is a cable
connector that is typically 2-3 inches long.

Hope this helps,
Roger


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## CWEISER (Jul 5, 2000)

Thank you Roger for the info on configuring a null modem cable. Do you know what keyboard/software commands would be required to copy File:x from C: #1 to C: #2?

Conrad


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## LarryCore (Aug 26, 1999)

Actually, a null modem cable acts like a modem. You need to run a terminal program on each computer to transfer files.

DOS may have a command that will work - a command switch on COPY maybe... but a terminal program would be a lot better. Windows 3.1 has a terminal program in it - just connect with the cable, go into the program on both machines and set it to connect via the COM port that the cable is on.

The just choose Send on one machine and Receive on the other.

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