🚀 go-pugleaf

On 09 Apr 1997 19:09:11 +0000, Graham Murray
<graham@barnowl.demon.co.uk> wrote:
>In article <5ieuo9$c6j@newsops.execpc.com>, stevem@execpc.com writes:
>> Nope!  X2 allows for *one* (and ONLY one) digital to analog
>> conversion in the path between the ISP and the X2 user.  As an
>> aside, more than one D/A conversion is the primary reason many
>> people will not be able to use X2 at all (and likely K546Flex as
>> well - if it ever actually gets released).
>
>Given that use of X2 requires that the 'master' site must be connected
>via ISDN, will there be many people who have more than one D/A
>conversion in the path?  With the telecos having fully digital
>backbones the only D/A conversion should be at the switch serving the
>user's local loop. Once the signal has been digitised at the local
>switch it makes no sense to add additional pairs of D/A and A/D
>conversions in the path, especially as the connection to the ISP is
>digital. 

	First off, telcos aren't all fully digital (although most
are), but more importantly, SLCs are becoming VERY popular in the U.S.
These may or may not cause a problem.  If they are digitally
integrated, then 56k PCM modems will work without any problems (and
should actually work quite well, since people on SLCs tend to have
less copper between them and the A/D conversion as compared to people
hooked up to a conventional telco CO).  However, if the SLCs are not
digitally integrated (which is fairly common), there will be an extra
A/D and D/A conversion in there, which will cause 56K PCM modems to
fail.  There are also problems with loading coils on lines which can
cause 56k PCM modems to fail.  All in all, it seems that about %20 of
phone lines in North America won't support X2 or K56Flex (very rough
estimate though).

Anthony Hill           |  Despite popular belief, this
ahill@travel-net.com   | is NOT a .sig file.