56k modems relied on digital trunk lines
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56k modems relied on digital trunk lines
1–10 of 143 posts
Re: 56k modems relied on digital trunk lines
#2Isn't it the opposite of the headline? Modems were hamstrung by digital phone lines you didn't know we had. One final trick allowed them to match, but not exceed, those digital lines.
Re: 56k modems relied on digital trunk lines
#3ah, good ol' capping out at 26.4kb/s...until 2005
Re: 56k modems relied on digital trunk lines
#4Isn't it the opposite of the headline? Modems were hamstrung by digital phone lines you didn't know we had. One final trick allowed them to match, but not exceed, those digital lines.
To me it looks like the article is largely told from the perspective of ISPs connecting themselves between each other, and how the constant analog/digital conversions between carriers were causing problems sustaining the 56k data rate that the (analog) last mile was always capable of... and how converting their internal systems and backhauls to digital solved that issue.
Re: 56k modems relied on digital trunk lines
#5That reminds me of my short time with ISDN and the amazing availability to receive calls on the second line without forcing me offline.
Re: 56k modems relied on digital trunk lines
#6That reminds me of my short time with ISDN and the amazing availability to receive calls on the second line without forcing me offline.
That 128Kbps on ISDN was the like the gold standard back then! I knew some sysadmins who had that installed to their homes so they could be available at any time. All paid for by the company they worked for.
Re: 56k modems relied on digital trunk lines
#7That reminds me of my short time with ISDN and the amazing availability to receive calls on the second line without forcing me offline.
I'm still mad that they high-quality voice audio possible through ISDN didn't become ubiquitous. It's ridiculous to hear the clipped frequency range of a plain old telephone line during radio interviews in 2025.
Re: 56k modems relied on digital trunk lines
#8That reminds me of my short time with ISDN and the amazing availability to receive calls on the second line without forcing me offline.
Indeed ISDN was amazing for its time but Ma Bell and her successor ILECs were way too proud of it so in the end it went nowhere and never made them all that much money.
If they had gotten out of their own way when the internet came around they could have charged a small monthly fee to upgrade to a "digital phone line". Lots of people would have switched.
Re: 56k modems relied on digital trunk lines
#9Isn't it the opposite of the headline? Modems were hamstrung by digital phone lines you didn't know we had. One final trick allowed them to match, but not exceed, those digital lines.
To me it looks like the article is largely told from the perspective of ISPs connecting themselves between each other, and how the constant analog/digital conversions between carriers were causing problems sustaining the 56k data rate that the (analog) last mile was always capable of... and how converting their internal systems and backhauls to digital solved that issue.
Exactly. More specifically, Internet servers in data centers connected themselves to the IP network, not the phone network (not surprisingly), so they almost always had an uplink significantly faster than 56 Kb/s. And the analog local loop had encodings that could transmit at 56 Kb/s. But these encodings were not compatible with the analog-digital conversion used in phone network backbone.
While today you'd probably expect that the IP network could connect to every phone branch office where the local loops were connected to the phone network, that wasn't necessarily the case - Internet data would usually have to travel some of its way over the phone network backbone, with the problematic digital encodings. V.90 and related standards allowed the phone network to accept the digital data directly from ISPs and send it in digital form to the branch office, without attempting a digital to analog to digital conversion to inject it as digital voice into the phone network. That's why the upload speed couldn't be improved via this method - it would still need to undergo analog-digital conversion to travel across the phone network to the ISP where it could enter the IP network. (V.92, a later standard, improved upload speed to 48 Kb/s via fancier signal processing trickery that could survive the digital voice conversion.)
Re: 56k modems relied on digital trunk lines
#10Yes these modems were almost-ISDN (minus the razor fast call setup). And required a full digital backend to work. They could only do 56k6 in one direction, to the user too. But they were made for internet access so that didn't really matter.