On Mar 12, 1996 at 06:32 hrs, Arthur Marsh of 3:800/812 wrote to Poe Lim:

Hello Arthur,

AM> For the best possible V.34 operation between a site with ISDN and a 
AM> remote site without ISDN, the ISDN equipped site should have a 4 wire 
AM> interface to its V.34 modem (either internally as Ascend presumably 
AM> does, or by having a 4 wire interface on the ISDN terminal adapter).

Why?  I don't see the difference that having the last few inches as 4 wire will make.

AM> Four wire analogue operation may also be easier to provide than ISDN 
AM> for remote sites that do need high speed data operation beyond 7 km 
AM> from the nearest exchange/RIM/RCM/...

Now this I agree with.  ALL long loop services should be 4 wire as this
allows the insertion of amplifiers without the problem associated with 2
wire amps.  I've always thought it was stretching the friendship to try
running bi-directional 2B+D services on a 2 wire circuit although the cost
of copper will always make telecom companies try.

I'd even like to see the situation where loops longer than xKm (or loop
loss greater than y db at 2KHz) MUST be 4 wire and have amps fitted at the
exchange and user ends to bring the losses back within spec.  While I am
pipe dreaming the amps should be equalized to give a flat response at the
receiving end.

Regards ... John
@EOT:

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