[ih] Nit-picking an origin story

[touch at strayalpha.com]

On Aug 24, 2025, at 2:15 PM, Clem Cole via Internet-history <internet-history at elists.isoc.org> wrote:
> 
> On Sun, Aug 24, 2025 at 10:43 AM Barbara Denny via Internet-history <
> internet-history at elists.isoc.org> wrote:
> 
>> You might hear 56 kb/sec from other people.  I was surprised to hear 50
>> kb/sec from this list somewhat recently.  Of course my memory could be
>> wrong but i always thought it was 56 kb/sec.  Did anything change by the
>> mid 80s? Your quotation says normally 50 kb/sec from the ARPAnet brochure
>> in 1980.
>> 
> That's because it was two very different technologies.
> 
> The earlier [circa 1970s] 50K links were created by "bonding" 12 dedicated
> analog voice circuits, and the reason they could not get more than the 50K
> was the overhead used for the mechanism used to make them appear as a
> single faster circuit.
> 
> In the 1990s, thanks to the microprocessor revolution, it became possible
> to use digital signal processing, and more than 1 bit could be sent at a
> time, so even though the Western Electric circuit under the covers only
> allowed 1200 BAUD, each BAUD contained more information.  

Bell101 was 110 bps and 1b/baud in the late 1950s.
V21 was 300 bps and 1b/baud FSK, in roughly the early 1960s.
Both were acoustically coupled, as were all customer equipment (i.e., not direct from the telcos) until the Carterphone decision in 1968.

By 1980, V22 supported 1200 bps using 2b/baud direct-wire via PSK.  I’m fairly sure - from opening them up at the time - that they had integrated circuits running the show internally. Commodity modems were doing 2400 bps using QAM by 1984 (I recall using one in 1985 when I started grad school). They hit 4800 bps by 1988.

By 1990, the transfer speeds were 9600 bps and many bits per symbol was common.

> Thus, a
> traditional voice-grade POTS line could send as fast as 56K bits/second.

56 K bps was V.90 in 1998, but unlike the other modes it wasn’t symmetric. It was 56K downstream and 36.6K upstream. The ISP side used PCM synchronized with telco digitation, but user equipment was given only analog transmit access and thus was limited.

Joe