> So here I am, trying to get my mac to output to serial (through the
> modem) to my pc (through its modem)...using a regular phone cord. I
> don't have a null modem cable, besides, I've got two different kinds
of
> hardware...they don't have the same type of connectors, though they do
> share the modems and phone cord...
>
> Both are running debian, and I know that I'm talking to the modem on
> each machine, but I can't get the one to output to the other. Or if it
> is, I can't tell...
>
> I'd like to know if it's possible to use a regular phone cord to have
> one pc output to serial to another pc. Can anyone help!
>
> TIA
>
> Russell
It sounds like you are trying to get the Mac to talk to the PC via
the serial ports. If these computers were running terminal
programs, they should link directly through the serial ports,
assuming those ports were connected through a null modem
cable, which is a multiple wire connector with either DB-9
or DB-25 connectors on either end (the Mac may not use
this type of connector, either, I am not sure. Sounds like that
is your case).
The multiple wires are needed because the hardware
handshaking lines (RTS-CTS and DSR-DTR) are involved.
There are several types of null modem cables depending on how
pins 4,5,6,8 and 20 are exactly interconnected. You can buy all the
parts needed to build one at Radio Shack. On a DB-25, when
wiring one connector end to the other end, use a lead for each:
connect 1 to 1 and 7 to 7, then connect 2 to 3 and 3 to 2.
Then connect 4 to 5 and 5 to 4. Then connect 6 and 8 together
on one end and run that lead to 20 on the other end, and
run 20 on the first end to 6 and 8 on the other end. This
is the commonly found pinout scheme, which looks
symmetrical if you draw it out.
Those are pinouts for a DB-25, you may need to get gender
changers and 9-to-25 adapters. (Easter than learning the
pinouts on a DB-9 after learning the ones on a DB-25...)
That all assumes the serial ports can talk directly.
If you get modems involved, then the Com ports talk to the
serial interface on each modem (assuming they are external
modems; if they are internal, then no serial lines are even
involved). The modems would talk to each other through a phone
cord, which can have just 2 wires, and in that case one modem
has to be able to be told to "dial" the other. Typically this can
be done by sending commands as part of the AT.. command set
e.g. ATDT1234567, ATH0, to each modem. This is OS-independent.
The modems have to be Hayes-compatible to understand
those commands. I don't think a Winmodem will be of use here,
as I don't think they support that firmware, but I have never
tried it. (I only have one modem here, a USRobotics)
In _any_ kind of modem work I believe it is essential to use
external modems so you can see the status lights, and look
at the voltages on the RS232 serial cables, to see what is working
and not working. It is not clear from your description, of what
exactly you are working with, hdwe-wise. A "break-out box"
is used to look at the signals on RS232, which are +12 and
-12 VDC and light a red or green LED on each signal line
to show the "1" or "0" line status. (Zero volts is not a valid
line status). RS has simple versions of this, as well.
The programs "tip" and/or "cu" would be the ones to look at for
support in configuring dialers, in Unix, and I expect work from the
command prompt only, as they are old enough to predate
usage of GUIs..
A "regular phone cord" won't work for serial data whenever
hardware handshaking (RTS-CTS) is needed. It MAY be made
to work if TD and RD are the only pins you need to send across
(pins 2 and 3) and software handshaking (XON-XOFF, or, ctrl-Q
and ctrl-S) are embedded in the data stream, which obviously
won't work for binary data). You should send signal ground
across as well (if not frame ground) so you're back up to
sending 3 wires across, and many "phone wires" today are
just 2 wires.
Break out boxes. The Abacus of Electronics.
HTH, - Bob
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