Re: News Tidbits

Ron Resnick (
Thu, 29 May 1997 13:00:29 +0300 (EET DST)

At 01:15 AM 5/29/97 -0800, you wrote:
>*** Transend delivers 67 kbps modem
>Transend Corporation advanced modem speeds to new heights, without the
>need for digital connections at either end, with their announcement
>Tuesday of the Transend Sixty-Seven, delivering speeds of 67 kbps both
>upstream and downstream, over existing analog phone lines. The
>Transend 67 solves the increasing speed and bandwidth problems of
>present-day Internet users, while utilizing the existing ubiquitous
>analog network. The Transend 67 also makes widespread, economical
>video teleconferencing possible for all sizes of companies. For full
>story, see

Interesting. But I'm confused ...

I thought there's a hard upper bound on what you can push through a POTS
line, simply because the line cards operate on a standard 64K channel
width, with 8K reserved for signalling, leaving an effective 56K channel.
Hence, no matter how much jazzy compression etc. the modem can do,
it does it no good to push more than the analog equivalent of 56K through
the line to the switch, because the line card won't push out more than 56
into the voice network. Isn't that the whole point behind ISDN? Ie, to
have the phone company physically replace your line card with an ISDN
card that can push you over the 56K barrier?

Modem<-----analog line (?? limit) -------->Line card----(56K
limit)---->voice network

Weakest link is 56K pushed out by line card to the switch, no?

Can someone please explain to me how this 67K magic works, or is
my amateur signalling theory all wrong....