56k modems relied on digital trunk lines
Dial‑up “56k” modems only reached their top speeds by exploiting the phone network’s hidden digital backbone, and were limited by how and where analog‑to‑digital conversions occurred. Commenters recall how ISP equipment, telco infrastructure choices (pair gain, repeaters, filters), and standards like V.90/V.92 and ISDN shaped real‑world speeds, latency, and availability—especially in rural areas. The thread also contrasts the theoretical capacity of copper with its messy real‑world deployment, and reflects on how those constraints pushed the evolution toward DSL, cable, and fiber.
Role of Digital Trunks in 56k Modems
- Several commenters argue the headline is slightly inverted: digital trunks initially limited throughput because voice-oriented A/D conversions mangled high‑rate modem waveforms.
- ISPs and servers were already on fast digital IP networks; the analog “last mile” could, in theory, carry ~56 kbps using special encodings.
- The problem was the phone backbone’s 8 kHz, μ‑law/A‑law, DS0/ISDN voice framing: multiple analog↔digital conversions broke the 56k signal.
- V.90‑style schemes worked by feeding digital data directly into the phone network at the CO and keeping it digital until the last analog hop.
- This only worked in one direction (downstream). Upstream still passed through traditional A/D paths, capping uploads at 33.6 kbps (later ~48 kbps with V.92 tricks).
Line Conditions and Real-World Dialup Speeds
- Many users recall being stuck around 26.4 kbps despite “56k” modems.
- Causes mentioned: extra A/D conversions, pair gain systems, bridge taps, load coils, narrowband amplifiers, echo cancellers, and generally poor outside‑plant copper.
- People describe telcos being unmotivated to fix lines for internet use; claiming fax problems sometimes forced them to re‑engineer circuits.
ISDN, Latency, and Early “Fast” Home Links
- ISDN (64 kbps per B‑channel, 128 kbps bonded) is remembered as a “gold standard”: low latency (sub‑20 ms), instant call setup, and simultaneous voice/data.
- Downsides: per‑minute billing, expensive tariffs, and deliberate discouragement by incumbents, which limited consumer adoption.
- Still heavily used for remote admin and high‑quality broadcast audio; some lament that today’s radio/phone interviews often sound worse.
ISP Gear and Numbering Tricks
- CO equipment often terminated multiple analog lines into racks of modems, later replaced by digital access servers that emulated many modems over a single T1.
- This digital termination on the ISP side was essential for true 56k.
- Toll‑free and nationwide dialup numbers were frequently routed to local POPs using intelligent-network routing based on caller location.
Copper vs. DSL/Fiber and Broader Reflections
- Commenters debate claims that “ordinary copper can do 1 Gbps”: technically plausible only over very short, clean runs; real loops with stubs, splices, and noise are far worse.
- xDSL is framed as using the same pairs but bypassing voice‑band constraints, with FTTN/FTTC seen as transitional before full fiber.
- Strong nostalgia for modem handshakes, “shotgunning” dual modems, Ricochet wireless, and the era when web pages had to fit within tens of kilobytes.