Dial Up Internet / BBS / Pizza

[Matthew]

Hello,

I've recently been playing with Dial Up Internet for "fun".

I've got two 56K US Robotics Modems. One works fine, the other refuses to connect or "Train Up". I've tried factory reseting it and copying over the AT commands and S registers, but still no dice. One observation, they sound very, very different:

Broken Modem

Working Modem

Does anyone have any ideas what the issue could be ( Bit of a long shot... ) ?

Secondly, with only a 50% success rate I'd quite like to verify it's actually working properly. Are there any retro computing aficionados with a modem on the list that'd be interested in coming to the space one evening and playing with Dial Up and possibly a BBS? There will be pizza.

Cheers

Matthew
Thanks

Matthew

[Adrian Godwin]

What are you testingh them against ?

I think I've still got a couple around : Pace and Motorola. However I think USR had their own private method before V42bis was standardised. It may be that one of them only does that method and will only work against another USR capable of it.

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[Adrian Godwin]

Wikipedia agrees, though it seems V42bis was later still.

https://en.wikipedia.org/wiki/Modem#Early_56k_dial-up_products

[Matthew H]

It's two Cisco boxes - one with a bank of digital modems and a PRI card, and the other with a PRI and FXS card. If I use another Cisco modem card as the client ( I forgot about that one in my original post ) I get a stable 44K down and 24K up

It's plausible it's doing something US flavoured although I have set the relevant bits to UK / UK Standards. (I've also tried setting it to the US in case that changes anything but no luck there)

I vaguely recall seeing something about their version of V42bis in the manual but as I copied the S registers over it should be disabled - I'll double check.

Cheers

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[Paddy Duncan]

It sounds to me like the oscillator is screwed, creating harmonics instead of the correct frequencies. It's trying to sing the right thing but is suffering from tonsillitis

Paddy

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[Ant -]

Not sure what the fault is but are these internal or external modems. I used the external US robotics modems because they just worked and there wasn't any stress getting them working where as every internal modem had faf with IRQ and memory ranges. I do still have a 56k 3Com US robotics modem in my collection although I've not powered it up in over 20 years and you would need a usb to serial port to connect it, or a 20 year old computer.

Kind regards 

Ant

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[Matthew]

Hi Ant,

All external, I didn't fancy messing around with PCI slots and drivers. They're similar in appearance to yours. They're both the same model but slightly different variants / part numbers.

Would you mind if I borrowed it for a week or two? Or I could bring the gear to the Hackspace to test it.

Cheers

Matthew

[Ant -]

Responded directly

Kind regards 

Ant

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[Yvan Janssens]

I have been doing this with some of the folks at https://shady.tel/, and we've got quite a few things online by now. Not everything is publicly routed so you will probably want to join the network.

There's loads of stuff in there:

- faxes

- BCM50s

- a PDP-11/73

- a S/390

- a pile of /400s

- a Sun 3/60

You should be able to experiment with at least faccs, PPP, shell accounts and SNA. If you're in a masochistic mood there's also infrastructure for ISDN. 

/y

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[Matthew]

Padski - Sorry I missed your post, yes it does sounds a bit off. I've cracked it open and there's no obvious bulging capacitors or anything which pretty much exhausts my troubleshooting. It wasn't expensive so it's not the end of the world.

Yvan - Yeah a few of the ShadyTel bunch have been helping out with the Dial Up side. I didn't realise there was a private network - I'd be interested in joining.

Cheers

[Dax Liniere]

This is so weird and supremely wonderful. :D

[Matthew]

Thanks Dax, I'll post some more info once it's done.

I managed to get the modem to connect by disabling v90. It then connects at 14.4kbs implying it's using V32bis. I'll take another look at the v.90 specific stuff at both ends and see if anything stands out.

Cheers

[Matthew]

In case anyones been wondering what happened with the dodgy modem, or has stumbled across this thread from elsewhere on the internet, I managed to get it working.

I had to set "compand-type a-law" on the voice ports, a-law being the standard voice codec used in Europe whereas u-law is more commonly used in the US. The cisco gear should infer the codec type from country settings elsewhere in the config, but in this case it didn't. It's not the first Cisco bug I've come across. I'm not entirely sure why it worked at all with the codec mismatch, I would have thought there'd be no audio at all. Presumably it was automatically transcoding, losing some quality in the process and affecting v.90 calls.

Anyway, if anyone wants to play with dial up internet or BBSs  give me a shout and I'll bring it in - I've managed to condense the setup down into a single router - only 3Us, 15kg and 120 watts idle ;) ... I'm still working on the blog post.

Cheers