<html><head></head><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px"><div id="yui_3_16_0_ym19_1_1484750757813_7391">John,</div><div id="yui_3_16_0_ym19_1_1484750757813_7393"><br></div><div id="yui_3_16_0_ym19_1_1484750757813_7395">The Bell 303 modem was specified to run at 50kbps. Your guess about DS0 sounds plausible for the underlying circuit speed but I don't know if it is correct.</div><div id="yui_3_16_0_ym19_1_1484750757813_7487"><br></div><div id="yui_3_16_0_ym19_1_1484750757813_7526">Cheers,</div><div id="yui_3_16_0_ym19_1_1484750757813_7528">Alex<br></div><div id="yui_3_16_0_ym19_1_1484750757813_7417"><span></span></div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1484750757813_7470"><br><br></div><div class="yahoo_quoted" id="yui_3_16_0_ym19_1_1484750757813_7532" style="display: block;"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;" id="yui_3_16_0_ym19_1_1484750757813_7531"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;" id="yui_3_16_0_ym19_1_1484750757813_7530"> <div dir="ltr" id="yui_3_16_0_ym19_1_1484750757813_7529"> <font id="yui_3_16_0_ym19_1_1484750757813_7534" size="2" face="Arial"> <hr size="1"> <b><span style="font-weight:bold;">From:</span></b> John Day <jeanjour@comcast.net><br> <b><span style="font-weight: bold;">To:</span></b> Paul Ruizendaal <pnr@planet.nl> <br><b><span style="font-weight: bold;">Cc:</span></b> internet-history@postel.org<br> <b><span style="font-weight: bold;">Sent:</span></b> Wednesday, January 18, 2017 6:11 AM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [ih] Arpanet line speed<br> </font> </div> <div class="y_msg_container"><br>I believe it was 56Kb. A DS0 out of a T1.<br clear="none"><br clear="none">John<br clear="none"><br clear="none">> On Jan 18, 2017, at 04:10, Paul Ruizendaal <<a shape="rect" ymailto="mailto:pnr@planet.nl" href="mailto:pnr@planet.nl">pnr@planet.nl</a>> wrote:<br clear="none">> <br clear="none">> <br clear="none">> I'm wondering about (early) Arpanet line speed. Online sources seem to say that it was 50kb/s on the long haul connections, provided by AT&T. To me, that "50" sounds like a strange number:<br clear="none">> <br clear="none">> - if the modem from the IMP to the Bell System was analog, the best technology of the time was perhaps 2.4kb/s (and this speed seems to have been considered initially). In this case a speed of 50kb/s is not a multiple of 2.4kb/s, and it would have required 21 parallel lines -- more logical would have been to use a full T1 connection and have 24 parallel lines or 57.6kb/s.<br clear="none">> <br clear="none">> - if the modem from the IMP to the Bell System was digital, it would most likely have used a single channel of a T1 connection, i.e. a 56kb/s rate. I suppose AT&T would have to run special lines from the IMP to the trunk, as I don't think digital lines were used for the last mile back then (perhaps they were to company/hotel PBX's, I don't know).<br clear="none">> <br clear="none">> Perhaps the "50" is a rounded number, perhaps some capacity is used for error correction, perhaps it is plain wrong.<br clear="none">> <br clear="none">> Does anybody have more background information on this?<br clear="none">> <br clear="none">> Thanks,<br clear="none">> <br clear="none">> Paul<br clear="none">> <br clear="none">> <br clear="none">> <br clear="none">> <br clear="none">> _______<br clear="none">> internet-history mailing list<br clear="none">> <a shape="rect" ymailto="mailto:internet-history@postel.org" href="mailto:internet-history@postel.org">internet-history@postel.org</a><br clear="none">> <a shape="rect" href="http://mailman.postel.org/mailman/listinfo/internet-history" target="_blank">http://mailman.postel.org/mailman/listinfo/internet-history</a><br clear="none">> Contact <a shape="rect" ymailto="mailto:list-owner@postel.org" href="mailto:list-owner@postel.org">list-owner@postel.org</a> for assistance.<div class="yqt9392446213" id="yqtfd57892"><br clear="none"><br clear="none"><br clear="none">_______<br clear="none">internet-history mailing list<br clear="none"><a shape="rect" ymailto="mailto:internet-history@postel.org" href="mailto:internet-history@postel.org">internet-history@postel.org</a><br clear="none"><a shape="rect" href="http://mailman.postel.org/mailman/listinfo/internet-history" target="_blank">http://mailman.postel.org/mailman/listinfo/internet-history</a><br clear="none">Contact <a shape="rect" ymailto="mailto:list-owner@postel.org" href="mailto:list-owner@postel.org">list-owner@postel.org</a> for assistance.<br clear="none"></div><br><br></div> </div> </div> </div></div></body></html>