RE: Modem Caller-ID question (long-ish)

[Keith Doxey <keith.doxey@xxxxxxx>]

Havent heard about it and any product that was sensitive to line polarity
would be permanently affected.

The only things I am aware of being sensitive to polarity are...
Earth Calling PBX's (usually large PBX's not smaller Key Systems although
some small systems are earth calling)

Old style 5p & 10p payphones (obsolete) that took all your strength to
put
the money in.
On these a line reversal would mean the slots were open until you needed to
put your money in at which point they would lock !

If a Caller ID device was affected by a line reversal it would either work
or not work.

You have indicated that your works for a while and then gives up.

Unless someone was changing the polarity of the line constantly that would
not happen, also reinitialising the modem would not make it work until you
had straightened out the reversal.

Also you have Home Highway, which if affected by line reversals would fail
completely. As the analogue ports are generated by the HH box I would ex
pect the polarity of those to remain the same irrespective of the actual
line polarity.

Some badly designed phones (read "not designed for the UK") can
be affected
by reversals.

The only real problems with the UK wing system is reversing the A & B
between sockets. This causes the following.....
socket 1	Bell connected between Bellwire & A - correct
AB reversal between socket 1&2
socket 2	Bell connected between Bellwire & B - wrong
the two bells are now effectively connected in series across the line and
will permanently seize the line and ring constantly (real bells will just
go ting and stick the armature of the bell hard agains the bell gong)
rendering the line useless.

There may well be some truth in what James has said but I dont believe its
the problem in your case.

Cant comment on the wiring of the cord as there are so many variations
especially for products designed outside the UK.

Hope that helps

Keith



> -----Original Message-----
> From: Paul Gordon [mailto:paul_gordon@xxxxxxx]
> Sent: 15 November 2000 19:58
> To: ukha_d@xxxxxxx
> Subject: Re: [ukha_d] Modem Caller-ID question (long-ish)
>
>
> Interesting,
>
> I presume you mean to the Line cord between the modem and the BT
socket?
>
> Do you know wich two? - there are 4 connected pins in a line cord
aren't
> there?
>
> Any input on this one Keith?
>
> Cheers.
>
> Paul G.
>
> >ISTR reading about a problem with polarity reversal on these
modems.
> >The cure was rumored to be to swap the 2 wires to the modem round.
> >Note that this is a mod to the modem cable, and not the BT wiring
on
> >either side of the master jack.
> >
> >After Hayes went bust, I looked around for a similar modem and US
> >Robotics told me that all of their Message Modems support BT
Caller
> >ID. Sadly work pressures has reduced my HA experimentation time so
I
> >didn't actually make a purchase.
> >
> >TTFN,
> >
> >James

>
>

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