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NULLMDM.ARK
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Text File
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2006-10-19
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2KB
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69 lines
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HOW TO BUILD A NULL MODEM
-------------------------
A NULL MODEM is nothing more than a
cable that alows two computers to
comunicate with each other by
connecting their serial ports together.
Using the apropriate software you can,
for example, pass the ascii files from
your TI-99/4A to an IBM computer or
from the IBM to the TI without using a
modem or phone lines. If you are
switching from one computer to another
this could be very handy item to have
around.
$4.00 to $8.00 dollars should be plenty
to by parts. If you have any spare
cables you may only need to move a few
wires around and spend no money at all.
I don't know how much they sell for in
the stores because I have never seen
one for sale but I'll bet it's a lot
more than this will cost to build.
The wiring is simple. Pins 2 and 3 are
crossed so that Transmit Data will be
connected to recieve data. Pin 4 is
jumpered to pin 5 and pin 6 is jumpered
to pin 8 on each connector. If you use
shielded cable the shield should only
be connected at one end to reduce
noise. If you know an electronics
engineer ask him to explain this to
you.
Once you have the null modem conected
between two computers they should act
as if they are connected through a
modem with one differance. The
computers can comunicate with each
other at as high a speed as their
serial ports will alow.
PIN# PIN#
1-----------1 GROUND(GND)
2-----------3 RECIEVE DATA(RD)
3-----------2 TRANSMIT DATA(TD)
4-- --4 REQUEST TO SEND(RTS)
| |
5-- --5 CLEAR TO SEND(CTS)
6-- --6 DATA SET READY(DSR)
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7-+-------+-7 SIGNAL GROUND
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8-- --8 DATA CARRIER DETECT(DCD)
PARTS:
2 DB-25 FEMALE SOLDER TAIL CONNECTORS
WITH HOODS
3 SECTION OF FOUR CONDUCTOR WIRE
4 SHORT PIECES OF WIRE TO JUMPER THE
PINS
TOOLS:
- small soldering iron 25W should do
fine
- small flat screw driver
- solder
-)UUUUUUUUUU
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