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From: "Carlos E.R." <robin_listas@es.invalid>
Newsgroups: comp.misc,alt.folklore.computers
Subject: Re: the early teletype
Date: Fri, 15 Nov 2024 14:42:25 +0100
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On 2024-11-15 00:11, Charlie Gibbs wrote:
> On 2024-11-14, Sn!pe <snipeco.2@gmail.com> wrote:
> 
>> Lawrence D'Oliveiro <ldo@nz.invalid> wrote:
>>
>>> On Thu, 14 Nov 2024 22:19:48 +0000, Sn!pe wrote:
>>>
>>>> Lawrence D'Oliveiro <ldo@nz.invalid> wrote:
>>>>
>>>>> On Thu, 14 Nov 2024 18:45:48 GMT, Charlie Gibbs wrote:
>>>>>
>>>>>> Original Teletype machines ran at 45.45 baud.
>>>>>
>>>>> I remember labels on Creed machines saying "50Bd".
>>>>
>>>> I had a Creed 7B 60 years ago, I used it for RTTY.  It had two
>>>> governers, one for 45.45 Bd, the other for 50Bd.  They had white
>>>> strobe marks on the circumference to set the speed accurately.
>>>
>>> Hmmm ... presumably the strobe marks were for use with a fluorescent
>>> light ... driven from AC mains frequency? Did they have different marks
>>> for 50Hz versus 60Hz mains?
>>>
>>> No, that wouldn't work, you would need entirely different gearing for the
>>> strobe wheel ...
>>
>> IIRC 50Bd was the US standard, most common in the rest of the world
>> was 45.45Bd  There was no gearing involved, the governor was attached
>> directly to the motor spindle and the strobe timing marks were on the
>> governors themselves.  I think (I'm not sure) that there were a
>> different number of strobe marks on either governor.
>>
>> I speak from personal experience but it was 60 years ago when I was
>> a teenager and memory is a tricky thing.
> 
> To further muddy the waters, 45.45 baud was just an average.
> Start and data pulses were 22 milliseconds long, while the
> stop pulse was 31 milliseconds.  (I guess the mechanism wasn't
> quite fast enough to process the received bits...)
> 
> Damn, the things one remembers...

They were in use at my time, somewhere, but I never saw one. Faxes were 
what they used.

Did teletypes use phone lines, with an audio coupler? Or dedicated lines?

-- 
Cheers, Carlos.