[ih] Arpanet line speed

[ats at offog.org (Adam Sampson)]

Paul Ruizendaal <pnr at planet.nl> writes:

> 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:

This has been discussed previously on this list:
http://mailman.postel.org/pipermail/internet-history/2004-February/000384.html

The August 1966 manual for the Bell 303 Wideband Data Station used to
implement these links is available from bitsavers, and gives a pretty
good description of how it works:
http://bitsavers.org/pdf/westernElectric/telephony/modems/

There are a number of mentions in there of "50 kbit per second operation
with a balanced interface for use with government cryptographic
equipment", which I assume explains the odd speed (but it really does
have a 50 kHz synchronous clock rate!). The other speeds it supports
look more like "round" numbers to the modern eye.

Thanks,

-- 
Adam Sampson <ats at offog.org>                         <http://offog.org/>