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Yes, once your call gets to the central office it's moved onto a digital connection -- essentially an ISDN line. Notably, the entire telephone network is stand
by tjohns 6y ago
Yes, once your call gets to the central office it's moved onto a digital connection -- essentially an ISDN line.
Notably, the entire telephone network is standardized on G.711 as a codec, which is raw PCM audio at 64 kbps, from 300–3400 Hz sampled at 8,000 samples/sec. (There's some regional differences that determine whether the network uses G.711u or G.711a, but that's not really important here.)
Also relevant: The digital telephone network is exclusively a switched (not packet-based) network, so you're guaranteed near-zero latency. This is particularly important for fax modems, which don't tolerate any jitter.
The end result is a connection that might not sound the best (due to the narrow bandwidth), but has call quality characteristics that are standardized and guaranteed across the network.
(At some point in the future the telephone network will upgrade codecs to G.722 and AMR-WB, which will give higher voice quality. This is the "HD Voice" feature you see on VoLTE phones. But it'll be a while before that's universal.)
- closeparen 6y ago>The digital telephone network is exclusively a switched (not packet-based) network, so you're guaranteed near-zero latency. Seems like this fact could be exploited more often in internet applications. High bandwidth channel for static assets, low latency channel for e.g. player movement data?
- bluesign 6y agoIt is already used with QoS [1] [1] https://en.m.wikipedia.org/wiki/Quality_of_service https://en.m.wikipedia.org/wiki/Quality_of_service
- Piskvorrr 6y agoWhich is traffic prioritization on the same channel. Having an extra link for high-priority traffic would be...exotic...but workable, sure.
- numpad0 6y agoOne of the professors when I was in a university was from ex-national telco R&D, and he was very vocal about those “real” bandwidth/latency/privacy assured telecom techs, “far superior” than “toys” like TCP/IP. And that was for the sake of education. He’d hold his lab meetings in Skype, not over a multipoint ISDN video calls on circuit switched wireless ATM. Only when the show is on, speaking to us undergrads through the mic, he declined to admit that IP is more adopted. Circuit switched data looks pretty on paper, that’s true, but at the end of the day no one pays for or bother with it.
- closeparen 6y agoLow jitter is a luxury for the document web, but if approximately all human social interaction is going to be through digital video for the foreseeable future, we might start to care...