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> DS1 (Digital Signal 1) out one end and a rack full of Zyxel modems on the other side

Why use real physical modems when you already have subscribers signals converted to convenient digital form in DS1 bundle? Wouldnt it make more sense to put a box with one fat DSP doing 24 modems all in bulk inside a box with DS1 and Ethernet sockets at the ISP location instead?

This did happen eventually. In the late 90's, various companies (Cisco, Ascend) provided boxes that could handle 24 modems on a single T1 port (PRI or channelized T1.) This massively improved ISP port density. Before that, it was racks and racks of modems...

IIRC it was the only way to support 56k.

Yes! The ISP side needed to be digital to get a 56K connection.

I was working for one of the telco equipment firms around that time. We made a box that would terminate TDM trunks and had it in the lab.

I was installing Windows 2000 on a PC in the lab (manual disk swapping required) when, hidden behind another rack, several shelves full of physical modems all started calling the box at once, speakers on.

I am trying to imagine the racket that must have made. Amazing how vivid that modem sound is in memory.

You're thinking about the Livingston/Lucent Portmaster 3. https://osmocom.org/projects/retronetworking/wiki/Livingston...

These were great boxes, and the only way you could get 56K was to call into an ISP with one of these or similar on their end -- the trickery that allowed 56K relied on one end being fully digital.

I was working for an ISP around that time and we had a bunch of Portmaster 2s connected via RS-232 cables to piles of modems, some rackmount some just stacks and stacks of US Robotics Sportsters. Sometimes modems would get wedged and we'd have to reboot them or "busy out" the line that they were on. Harder for the modems that were an hour away.

When the transition happened we were able to get rid of all those wires and just plug in one small phone cable for the T1, another for Ethernet, and terminate 23 lines. The Portmaster would treat all the modems as a pool and route calls to whichever was available, and once a call was done would run some testing on the modem before putting it back into the pool. It was like a space age rocket ship! At one point I was driving around with $50K worth of Portmasters in the trunk of my car, hoping I didn't get rear-ended. They were not at all cheap, but they were worth it.

Similar story with Portmaster 2s and a wall of modems layed out. The resulting blinking lights acted like a load monitor of sorts as the activity would spread across the wall as customers dialed in after work and signed off at night. Not mention a wall of flashing red lights made a pretty good picture of ‘the internet’ for those just starting out on this adventure in 1997.

Oh man. I was talking to my wife’s acquaintance and he was excited to talk shop when he found out I was technical. He worked at “this small company you’ve never heard of, Livingston.” “As in, Portmaster?” “You know about that?!”

Yeah, friend. I’m very familiar, and it was amazing tech. It sure kept the data center cooling system busy, though.

Revealing my ignorance here, but was (is?) there a telephone equivalent of anycast such that, say, the 1-800-... Or 1-900... numbers would be routed differently based on location? My basic knowledge of phone systems suggests it would at least be possible.

Absolutely, when call hits local switch it can be terminated differently based on its location. Particularly pertinent for modem based services in the 90s. A single national dialup number would terminate on 100s of local pops and routing decisions would be done to keep traffic as local as possible.

Internet Thruway from Nortel allowed multiple ISPs to use the same local termination hardware; If I remember the details correctly, different national numbers could be terminated on the same box, with the subsequent IP traffic routed to the correct ISP.

Wikipedia has good info on how RespOrgs handle this:

https://en.wikipedia.org/wiki/Toll-free_telephone_numbers_in....

Yes, the Intelligent Network was the big thing in the 1990s. It allowed for routing as you describe as well as calling cards and many other features: https://en.m.wikipedia.org/wiki/Intelligent_Network

Oh the joys of watching terminal logs with SS7 data frames!

Was there any way for the customer to somehow interact with SS7 frames?

We’ve had techs come to our home in Canada in the 1990s, and I remember being fascinated with their mystical toolbox phone that seemed to uncover hidden phone line functionality. Almost like the whip in Indiana Jones.

I don't think so, but who knows. In my case I was working at a telco so everything was very obvious at the dev environments.

911 and 0 (operator).

Yes, but it would usually be based on the first 3 or 6 numbers of your phone number. The first 3 are of course “area code” and the 6 are called “NPA-NXX”. This has blurred some due to line number portability and cell phones.

Yes, at the very least 911 (US) / 112 (EU) run on that system. For SIP numbers routing depends on the address you set up in the phone provider's portal, so if you're using bring-your-own-SIP to provide landline phone service in your house, you absolutely have to keep the address current or you risk dialing 911 and ending up on the dispatch of your old addres...

Not in the US, but we had a country-wide number that each local station simply routed to a local extension. Sometimes, even multi-line wasn’t available at some stations, so it was just a sequential list of extensions to try. Looks like a hack, but it worked flawlessly.

Isn't DSL basically the same thing? If you live in a jurisdiction with unbundled local loops (which I suspect you do not), your phone company terminates your DSL at their nearest "office" (often a roadside equipment cabinet nowadays) and then does Metro Ethernet over the phone company's data lines to your ISP.

If you don't live in that jurisdiction, it's the same but your ISP and your phone company are the same company.

Also you don't dial your ISP with a number.

Compaq Presario catching strays.

>I know that between around '93 and '97 if you dialed AOL from D/FW there was a good chance your call would be terminated somewhere within a mile or two of your house and the bits flowing between your Compaq Presario and AOL would be sent digitally from the local CO to AOL's data center in Sterling, VA.

Around the end of the dialup era, I noticed a bunch of similar low cost dialup services all used the same phone numbers, is this part of the reason, or were they all just reselling the same internet access or something?

Not GP, but this reminds me of how modern GPON (including XGS-, 50G-) works in some areas, like NBN (Australia), NTT FLETS (Japan) and Openreach (UK) where the fiber runs, on what is essentially, a PPPoE or IPoE pipe that tunnels the connection from the customer to the real ISP the user subscribed. Switzerland (basing at least on Init7 docs) has somehow decided on fiber-optic being a real dumb pipe, which is really nice but I imagine that it is costly.