A dialup ISP in your basement?

[TandyMan100]

I've got a couple of old computers and laptops that would be great fun to network. The only problem here is their only networking hardware is dial-up modems. Would there be a way to take an old PII or PIII system and set it up so that I can plug in vintage systems to its dialup modem and have it emulate an ISP? The idea here is a bridge to the modern 'net with the client computer thinking it's connected to a period dial-up ISP.

Hope I explained my intentions clear enough.

 

[chalackd]

I seem to remember using the basic circuit described here, powered with a 9v battery to get a couple computers to talk to each other. I don't however remember if I actually managed to transfer a file, or if I had only got them to connect...

 

[NeXT]

There are of course phone line emulators but thosre are remarkably expensive.

 

[Ole Juul]

Is it absolutely essential that there is a dialtone? If not, why not just plug one computer modem into another computer modem using a regular phone wire?

BTW: I don't think this has much to do with running an ISP

 

[RickNel]

If I understand you correctly, then the Freesco software router will do what you want. It is a well-maintained open-source project with modules that acts as router, firewall, server, and dial-in server depending on how you choose to configure it through a very simple interface. I used it for years. It will run easily on any PII with modest memory.

So long as the host machine has a modem port (usually RJ11) and an ethernet port (usually RJ45), you are in business. I always had two ethernet ports - one for the LAN, one for the Internet.

I've made modem-to-modem connections without needing any special interface circuitry - the modems just negotiate with each other in the normal way using the AT instruction set.

Rick

 

[Old Computers]

Instead of using a modem and phone emulator, you could try using a parallel port ethernet adaptor. Good luck with your project!

 

[TandyMan100]

If I understand you correctly, then the Freesco software router will do what you want. It is a well-maintained open-source project with modules that acts as router, firewall, server, and dial-in server depending on how you choose to configure it through a very simple interface. I used it for years. It will run easily on any PII with modest memory.

So long as the host machine has a modem port (usually RJ11) and an ethernet port (usually RJ45), you are in business. I always had two ethernet ports - one for the LAN, one for the Internet.

I've made modem-to-modem connections without needing any special interface circuitry - the modems just negotiate with each other in the normal way using the AT instruction set.

Rick

Looks nifty! Will this let the vintage systems in question connect to the Pentium II the same as, say, AOL dial-up internet?

 

[RickNel]

Looks nifty! Will this let the vintage systems in question connect to the Pentium II the same as, say, AOL dial-up internet?

Not quite the same because a) you can use the connection more like a LAN connection, and b) you will not need the commands that dial the telephone number. The modem on the initiating machine will negotiate directly with the modem on the host/router when it receives the appropriate instructions.

Google "AT modem commands" for plenty of explanations on how to set it up for interactive console usage or putting commands in a batch file or script, depending on the operating system. You may also need to set up PPP or SLIP protocols.

Freesco's dial-in server just listens for AT commands, it doesn't care about phone companies. There's an active forum on the Freesco.org site that can give more up to date advice than me.

Rick

 

[TandyMan100]

Awesome, I'll look into it. Thanks!

 

[rorypoole]

when I was in college I built a phone line simulator for fun, I using 555's and relays, it had the correct ring timing and could detect when the phone was off hook, ect, but I never did get the dtmf decoder chip to work sadly, and it did need a 12v and 36 to 48v dc supply.
why dont you get an old analog office phone exchange?

 

[Chuck(G)]

An old KSU may do exactly what you need. Most of the later ones used MCUs and could be reprogrammed.

 

[glitch]

An old KSU may do exactly what you need. Most of the later ones used MCUs and could be reprogrammed.

Yes, a KSU would be able to provide talk battery and ringing voltage. The old electromehanical 1A2 KSUs are a trip...fun to work on, or at least I think so. You still have to trip the ring detector, but if you were hacking one together you could add a "ring the line" button.

In any case, you do need at least talk battery (around 24 VDC) to send any sort of sound over a telephone wire, and a ring generator (120 VAC, 20 or 30 Hz depending on a number of things, anything in this range works) if you want to actually ring the destination modem. You don't need to generate dialtone even for most Hayes-compatible smartmodems, though you may need to change your dial command to ignore the lack of dialtone.

Something I've experimented with is using Asterisk with a hardware analog card. This should work especially well if your calls are staying local (not going out over VoIP). Older hardware is pretty cheap nowadays.