[Gllug] WiFi modem / routers etc - recommendations for increased range please!

[James Courtier-Dutton]

2009/6/18 John Winters <john at sinodun.org.uk>:
> You make it sound like ADSL is an alternative to ISDN.  It's more correct
> to think of ISDN as an alternative to POTS.
They are all grouped together ADSL, ISDN, POTS. They all work over
twisted pairs.

>
> ADSL is designed to work in addition to an existing telephone connection -
> either POTS or ISDN.  BT claim that offering both POTS+ADSL and ISDN+ADSL
> would cause unacceptable interference, and so offer only POTS+ADSL.
> ISDN+ADSL is commonly available in other countries though.  It has
> significant advantages - two simultaneous conventional calls, rock-solid
> digital connection etc.
POTS+ADSL uses different technology than ISDN+ADSL.
ISDN+ADSL reduces the bandwidth available to ADSL and thus ADSL with
ISDN has lower data transfer rates for the ADSL bit.

>
> We were rather behind in the implementation of ISDN when ADSL came along,
> and given BT's refusal to offer both together it has rather killed the
> market for ISDN, but arguably we're the ones who are using old technology
> in the UK with POTS+ADSL.  More advanced countries offer ISDN+ADSL.

Because it was too expensive for BT to implement. At the time, running
POTS+ADSL required different hardware at the exchange than running
ISDN+ADSL, and BT did not see a business case for doubling up on cost
of providing ADSL to customer. In fact ISDN+ADSL is rather a pointless
combination, because one could run more than 2 voice circuits over
ADSL if one wished. It is ATM after all and Voice-over-ATM was thought
to be a good idea at the time. Of course, VoIP over-took that idea.
Another driver was problems that any DSL technology brought to BT in
the form of lost revenue. An ISDN line rental cost far more than a
POTS+ADSL line rental, but POTS+ADSL provided more data bandwidth than
ISDN did and many customers saw the benefits that POTS+ADSL had over
ISDN. So, a lot of BT customers moved from ISDN to POTS+ADSL resulting
in a lot of lost revenue for BT.

Kind Regards

James
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