WPPLTD.DEMON.CO.UK - still up to date?

On 26/12/2011 17:51, Jon wrote:
> Hello all,
>
> I Know Peter Parry used to be around these groups and hosts this site,
> regarding specifically UK telephone wiring.
>
> Tell me, is the info contained herein still up to date?
>
> http://www.wppltd.demon.co.uk/WPP/Wi...telephone.html
>
> If Peter himself is still around perhaps he could comment?
>
> Reason for asking, my folks broadbad is up the shoot. Router shows no
> sync on any of the extensions in the house, but works in the test socket
> on the BT master. All filters have been swapped etc, no effect. I
> therefore diagnose a fault somewhere in the house.
>
> Unless someone want to advise me different?
>
> Thanks and regards
> Jon Parker
>

You could try this. Remove all your filters and plug the phones etc
directly into their respective sockets. Now take one filter of the
"dongle" type that has a short piece of cable to the
master socket, remove the faceplate and plug it into the test socket.
Plug your router into the RJ11 and plug the faceplate bodily into the
phone socket on the filter (hopefully there is enough slack in the wiring.
There, you've fixed it! Looks a bloody mess but functionally your
installation is the same as fitting a faceplate filter, and once you
have POC you can buy a proper one.

--

Graham.

%Profound_observation%

On Mon, 26 Dec 2011 23:47:09 +0000, Graham. wrote:

> You could try this. Remove all your filters and plug the phones etc
> directly into their respective sockets. Now take one filter of the
> "dongle" type that has a short piece of cable to the master socket,
> remove the faceplate and plug it into the test socket. Plug your router
> into the RJ11 and plug the faceplate bodily into the phone socket on the
> filter (hopefully there is enough slack in the wiring. There, you've
> fixed it! Looks a bloody mess but functionally your installation is the
> same as fitting a faceplate filter, and once you have POC you can buy a
> proper one.

Caution - not all dongle filters have enough capacitance to properly
support multiple ringers. The capacitor may get warmer feeding multiple
ringers than it would feeding a single ringer.[1]

You need about 470pF / ringer, or 1.8uF for 4, some dongle filters only
have 470pF caps fitted for the ringer.

As the suggestion above replaces the 1.8uF cap in the backplate with the
one in the dongle, you should be aware of this potential issue (the only
way to check is to open the dongle and trace the circuit).

Mind you, I took the bell caps out of my dongles anyway, as my phones are
proper 2 wire devices (most modern phones are) rather than 3 wire relics.

Hint to the OP - if all the phones are 2 wire devices, when you re-wire,
just use pins 2 and 5 throughout. Put a sticky label on the outside of
the master socket saying something like "2 wire phones, bell wire not in
use."

Rgds

Denis McMahon

[1] Normally R of 1 ringer and C of capacitor are in series with an
assumed constant ac V ringing supply. If you add extra phones, the R
component reduces to R/n where n is the number of phones, so total series
impedance drops, and more current is drawn from the ringing supply, this
current all passes through the C, which develops a higher voltage drop
proportional to current and reactance (reactance is a function of
frequency, so is constant as ringing frequency is constant). More current
draw and more voltage drop all adds up to more power dissipated in the C!

On 27/12/2011 01:45, Denis McMahon wrote:

> Caution - not all dongle filters have enough capacitance to properly
> support multiple ringers.

True - they're only meant to feed one device - a REN of 1, or 1.5 at a push.

> The capacitor may get warmer feeding multiple ringers than it would
> feeding a single ringer.[1]

Bzzt, heating of the capacitor is a complete non-issue.

> You need about 470pF / ringer, or 1.8uF for 4, some dongle filters only
> have 470pF caps fitted for the ringer.

Bzzt again, you need 470 nF (= 0.47 uF). 470 pF is three orders of
magnitude too small!

> [...]
>
> Mind you, I took the bell caps out of my dongles anyway, as my phones are
> proper 2 wire devices (most modern phones are) rather than 3 wire relics.

Why bother to remove the caps? With a 2-wire device there's simply no
connection to the capacitor anyway.

--
Andy

On Tue, 27 Dec 2011 23:33:38 +0000, Andy Wade wrote:

> On 27/12/2011 01:45, Denis McMahon wrote:
>
>> Caution - not all dongle filters have enough capacitance to properly
>> support multiple ringers.
>
> True - they're only meant to feed one device - a REN of 1, or 1.5 at a
> push.
>
>> The capacitor may get warmer feeding multiple ringers than it would
>> feeding a single ringer.[1]
>
> Bzzt, heating of the capacitor is a complete non-issue.

I'd not bet that there isn't somewhere out there a dongle filter
manufacturer whose dongles use minimum spec components - and in those
heating of the cap could be an issue.

>> You need about 470pF / ringer, or 1.8uF for 4, some dongle filters only
>> have 470pF caps fitted for the ringer.

> Bzzt again, you need 470 nF (= 0.47 uF). 470 pF is three orders of
> magnitude too small!

Yep, that was a mistake on my part.

>> Mind you, I took the bell caps out of my dongles anyway, as my phones
>> are proper 2 wire devices (most modern phones are) rather than 3 wire
>> relics.

> Why bother to remove the caps? With a 2-wire device there's simply no
> connection to the capacitor anyway.

Because if you have dongle - flat extension lead - phone, then the ring
wire in the flat extension lead is a long line antenna.

That gives a path for RF interference back into one leg of the pair
through the bell capacitor. Some dongles[1] even have the bell cap
upstream (i.e. line side) of the rf filter, and have a very simple rf
filter implementation.

The same applies if you have a 2-wire device on a 4-wire line cord.

Injecting RF into one leg of the pair is a sure fire way of increasing
the noise on the adsl line.

Now it may not be necessary in most cases, but in my book, every little
bit of noise reduction helps.

Rgds

Denis McMahon

[1] I've only taken maybe 40 or 50 apart so far, and most of them had the
bell cap on the downstream side of the rf filter, but some of them, maybe
between about 5% and 10%, have the bell cap upstream of the rf filter
(they also tend to have a very simple rf filter, often pi with a single
choke in only one leg, so they're crap filters anyway).

In article <4efa6b5b$0$16537$(E-Mail Removed) >,
(E-Mail Removed) says...
>
> On Tue, 27 Dec 2011 23:33:38 +0000, Andy Wade wrote:
>
> > On 27/12/2011 01:45, Denis McMahon wrote:
> >
> >> Caution - not all dongle filters have enough capacitance to properly
> >> support multiple ringers.
> >
> > True - they're only meant to feed one device - a REN of 1, or 1.5 at a
> > push.
> >
> >> The capacitor may get warmer feeding multiple ringers than it would
> >> feeding a single ringer.[1]
> >
> > Bzzt, heating of the capacitor is a complete non-issue.
>
> I'd not bet that there isn't somewhere out there a dongle filter
> manufacturer whose dongles use minimum spec components - and in those
> heating of the cap could be an issue.
>
> >> You need about 470pF / ringer, or 1.8uF for 4, some dongle filters only
> >> have 470pF caps fitted for the ringer.
>
> > Bzzt again, you need 470 nF (= 0.47 uF). 470 pF is three orders of
> > magnitude too small!
>
> Yep, that was a mistake on my part.
>
> >> Mind you, I took the bell caps out of my dongles anyway, as my phones
> >> are proper 2 wire devices (most modern phones are) rather than 3 wire
> >> relics.
>
> > Why bother to remove the caps? With a 2-wire device there's simply no
> > connection to the capacitor anyway.
>
> Because if you have dongle - flat extension lead - phone, then the ring
> wire in the flat extension lead is a long line antenna.
>
> That gives a path for RF interference back into one leg of the pair
> through the bell capacitor. Some dongles[1] even have the bell cap
> upstream (i.e. line side) of the rf filter, and have a very simple rf
> filter implementation.
>
> The same applies if you have a 2-wire device on a 4-wire line cord.
>
> Injecting RF into one leg of the pair is a sure fire way of increasing
> the noise on the adsl line.
>
> Now it may not be necessary in most cases, but in my book, every little
> bit of noise reduction helps.

Gents, some superb tips there. Thanks for the 2-and-5-only suggestion
Dennis, they have three handsets (two of which are cordless, don't ask
me why) and all are a modern type.

Regards
Jon