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I think this fits the mood. The old telephone system was entirely analogue. It remained so well into the 1980s, even when they were carrying tens of thousands
by retrac 5y ago
I think this fits the mood. The old telephone system was entirely analogue. It remained so well into the 1980s, even when they were carrying tens of thousands of conversations in parallel on a single wire or antenna.
When I was a kid, you could hear the white noise stack successively louder on a long-distance call, as it went through each additional link. And sometimes you could hear the hum of it all, just below the threshold of intelligibility. In hindsight it's amazing how well it all worked.
But sometimes it didn't work so well: https://vocaroo.com/1oCxkWyNDusp https://vocaroo.com/1oCxkWyNDusp
Maybe a filter was slightly out of tune on that day. Recorded mid-1970s New York. The electronic beeps are in-band call establishment tones. (Yes, the same ones phone phreaks exploited. The recording was in fact made by one of those phreaks who has gone back and narrated some of his old recordings http://www.evan-doorbell.com/ http://www.evan-doorbell.com/ )
- deleted 5y ago[deleted]
- jibcage 5y ago“Hello? Yes, a collect call for Mrs. Floyd from Mister Floyd Will you accept the charges from United States?” I always wondered what those beeping tones were in the recording at the end of that song (“Young Lust”). I guess I’m not old enough :)
- TedDoesntTalk 5y agoThose are in-band signals to the switching equipment. The equipment would “hear” those tones and translate them into “machine instructions”. That’s why phreakers could exploit the system by generating those tones themselves and playing them into the phone microphone.
- jeffrallen 5y agoThat's why you do not control networks with signals on the network itself. See also: Facebook's recent outage.
- TedDoesntTalk 5y agoRight. But those were different times. And the bandwidth of analog lines was something like 4 kHz with no control channels.
- packetslave 5y ago> That's why you do not control networks with signals on the network itself. Other than, you know, the entire Internet (BGP) and pretty much every corporate WAN (OSPF, EIGRP, RIP) and LAN (spanning tree, ARP). Having an out-of-band control plane is very much the exception. Now OOB emergency access, on the other hand... edit okay, SS7 is out-of-band, but parent was talking about IP networks.
- TedDoesntTalk 5y agoI don’t know about that. Even the ancient FTP protocol has a separate control channel/port.
- icehawk 5y agoAnd even with those things being in-band, we now have authentication for BGP and the IGPs to try and constrain the ability to send control signals. SS5/CCITT5 would probably have played out a lot differently had they hand the ability to do that sort of thing like we do now.
- deleted 5y ago[deleted]
- TedDoesntTalk 5y ago> But sometimes it didn't work so well: https://vocaroo.com/1oCxkWyNDusp https://vocaroo.com/1oCxkWyNDusp Huh. I never heard that in the 70s and 80s. Cool.
- tenebrisalietum 5y agoT1s are not analog and they were either invented or starting to be deployed in 1962.
- riffic 5y agothere were previous systems in place before T-carrier: https://en.wikipedia.org/wiki/Carrier_system https://en.wikipedia.org/wiki/Carrier_system https://en.wikipedia.org/wiki/L-carrier https://en.wikipedia.org/wiki/L-carrier http://long-lines.net/tech-equip/misc/J-Carrier.html http://long-lines.net/tech-equip/misc/J-Carrier.html
- jimmaswell 5y agoI found a youtube channel with a lot of interesting recordings of the old phone system. https://www.youtube.com/watch?v=eiQ2MwMdYPk https://www.youtube.com/watch?v=eiQ2MwMdYPk