Modem Collection

From: Allison J Parent <>
Date: Fri Jul 11 13:24:48 1997

> From: Marvin <>

> Just curious (again!) if anyone is collecting the early modems used on
> computers and what might have been the earliest commercial phone modem.
> I have several devices that are called modem eliminators and I believe
> these are basically serial cable boosters to increase the permissible
> cable length. My guess is that the earliest modems were accousticle
> (sp?) modems where the coupling was where the phone was laid onto the
> modem rather than a direct connect to the computer. Was there anythin
> earlier or other type of device?

Early modems were mostly acoustical as it was a way of avoiding the BELL
TELEPHONE CO tarriff and interconnection restrictions. There were also
direct connect bell103 is well known of them. They go way back, to the
old rtty machines used during WWII maybe before. Yes, those would have
vacuum tubes.

The modem eliminators were rs232 or current loop to rs422 which could be
used up to several thousand feet or more. These were not modems per se
but level translators to a format that worked well on hard copper pairs
at what would be then called high speeds (4800 ->38.4++).

Received on Fri Jul 11 1997 - 13:24:48 BST

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