Hello everybody,
I didn't know were to post this, so i posted here in hardware section.

I'm having some troubles while trying to interconnect two pc's via modem (soft fax modem, RJ-11 jack). One is a Handheld PC (HP Jornada 728) with a single fax modem slot, and the other computer is a PC with a two-slots fax modem (in/out).

I connect a phone cord to the HPC jack and the other end to the "in" jack of the PC's modem. My problem is that the connection requests me a PHONE NUMBER to dial, but, since it's a direct local connection between two computers, there's no phone number at all. I've tried everything, connecting to the "out" phone jack, connecting a phone line to the "in" jack and dialing its number from the HPC, dialing numbers such as "1", "123", hyperterminal, minicom, AT commands like "atd" and "ata" on the other end getting "NO CARRIER" as response after modem characteristic sounds, etc. And nothing seems to work.

Indeed, i read something about using a line simulator to get the phone cord a determinated voltage and amperage to one of the cables (the geen one) to fake a phone line. I constructed the simple device it displayed in the article, and couldn't get it working.

Could someone tell me or guide me on how to stablish a successful connection between this two computers via modem? Like how should i connect the modems and how to configure them.

The PC has both operating systems, Windows and Linux, i'd prefer the setup from the Linux environment, but if you could make it from Windows, excellent for me too.

I need to transfer data between the two hosts and is possible, share PC Internet connection with my HPC. The fact is that my HPC doesn't have other way to connect (no serial cable, no USB cable, no PCMCIA network cards, ...) So this is my last resort.

Any help will be appreciated.
Thanks in advance.

If the sockets are both RJ11 I assume that both expect to be connected to a phone line and "hear" a dial tone when they connect to the "line".

You don't say what country you are in but modems can have variable standards. You need to know that they are both the same.

Can you connect both devices to real phone lines or on extensions of a PBX that uses POTS phones? Then dial the other number or extension number. With appropriate AT commands you can set one to auto-answer and the other to dial the number (or extension number) of the other.

How much data do you want to transfer? Too much to make a public network phone call to do it?

You can't connect two modems jack-to-jack and expect them to work, you're missing something important, the telephone company. You'd need something odd like long-haul modems to connect without a telco.

I read an article in a magazine long ago -- might have been Popular Electronics -- schematics for a device which would do this; a sort of telephone-company-in-a-box. It would generate dialtones and react to a number being dialed on one end by ringing on the other, but it was a big and complicated device due to the high voltages needed to drive telephone lines and the complexity of having to understand DTMF audio. They could probably miniaturize it further these days, but most hobbyists don't care about POTS anymore.

It was the "Telco in a Box", in the 1995 issue of Electronics Now. Unfortunately I don't have that anymore, and don't see the article available online anywhere.

I doubt whether there is a connection (excuse the pun) but Telcoinabox is a wholesale telecoms company headquartered in Australia and operating globally. Perhaps their device??

The HPC has a serial port (according to the spec sheet) Use a null modem cable and connect to the serial port of the PC. On a 25 pin serial cable, connect 7 to 7 and cross 2 and 3. On a 9 pin connector, cross 2 and 3 and 5 is straight through. Set the baud rate at 38400 first, if there are errors start lowering it.
PC serial port (RS-232 DE9) pinout and wiring @ pinouts.ru

You would have to find PPP software for the HPC in order to have the pc connect to the internet.

Yup, this is a great solution.