1964 Antique MODEM Live Demo
chrise at pobox.com
Fri May 29 07:34:35 CDT 2009
On Thursday (05/28/2009 at 04:03PM -0700), Brent Hilpert wrote:
> (pedantic: His technical description was a little off, it's FSK, not an
> 'interrupted' tone.)
Agreed. He started to get on track but then fell off again when he started
saying the tones were a function of the voltage level coming in on the
RS232 port and that because his laptop had too low of a voltage on that
port, he was getting the wrong tones. This whole discussion in the context
of the modem being analog-- implying that he was getting tones that were
off frequency due to the incorrect voltage level. I don't think it went
quite like that.
> Does anyone know if the frequencies for the 110 and 300 baud modem standards
> were the same or different?
They were the same. Bell 103 tones...
I have several early Multi-Tech acoustic couplers here... FM300 which
was indeed analog-- done entirely with opamps as active filters and
then FM30 which was Multi-Tech's first digital discriminator design.
I spent a fair number of my formative years working at Multi-Tech. I was
there when the FCC ruling changed allowing customer owned equipment to
connect directly to the phone line. That was a big day... and almost
instantly spelled the end of acoustic couplers :-)
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