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ADSL "bell wire filter"

Started by gpo706, April 16, 2011, 06:36:25 PM

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gpo706

Didn't know where to post this so it ended up here.

Can anyone explain how this gadget works?

We have had terrible broadband on ADSL since we switched back to BT (though not as bad as AOL), then I got one of these for less than 8 quid and rewired the faceplate and the BB speed is much much better.

I'm glad I did, because my brother is on one of the hubs and he was harbouring suspicions my Pana PBX was slowing it up, anyway seems to work plenty now.

BTW - BT actually offer you a "free" one of these in the small print if you sign up to a 2-year contract, darn sharp practice in my opinion they should supply them as standard when you sign up, bloody rip off.

The new faceplate has three terminals the old six though only through a three wire input.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=260653410511&ssPageName=STRK:MEWAX:IT





"now this should take five minutes, where's me screwdriver went now..?"

Owain

In a normal telephone installation a pair of wires goes from the exchange to your master socket. From there people often have extension wiring which is 3 wires to every extension. The extra wire is the bell wire.

Up until the master socket the wires are balanced 2-wire twisted pair which, in simple terms, stops them losing as much of the ADSL signal as it goes along the wire and also stops as much interference getting in to the wire. The bell wire in your house makes this un-balanced and allows more interference in to the wiring. The normal filters you use for connecting ADSL and telephone only filter out the telephone as a cause of problems. They do not filter the bell wire which can go for many metres around your house (near electrical wiring and equipment that could cause interference).

The solution is to filter the bell wire at the master socket. A normal faceplate splitter will do this, but is not always convenient for people wanting ADSL connected somewhere other than their master socket because the faceplate blocks the ADSL to all downstream extensions.

Modern phones often don't use the bell wire at all for ringing, leaving it floating in the air as a giant aerial.

gpo706

#2
As a succinct answer as I could wish Owain, so basically BT are ripping you off with a 2 - year contract to get a bit of kit to make their darn BB service actually work.

Now gonna email this to my brother and press his face to the screen and make him read it   ;)

Many thanks for the explanation.

BTW should I get a surge protector or mains filter for the router, it still has disconnects?
"now this should take five minutes, where's me screwdriver went now..?"

Phonesrfun

I never did understand why the UK and other Euopean countries systems were wired to split the ringer wire off at the main jack.  Was it so that in the olden days of party-line ringing, it could be wired properly at the main jack and then every phone in the house was standardized (standardised), as opposed to the US method where each phone in the house had to be wired properly for party line ringing?

Surely it was not to save the cost of a ringer capacitor in each phone?

-Bill
-Bill G

Owain

Quote from: Phonesrfun on April 16, 2011, 08:06:58 PM
I never did understand why the UK and other Euopean countries systems were wired to split the ringer wire off at the main jack.  Was it so that in the olden days of party-line ringing, it could be wired properly at the main jack and then every phone in the house was standardized (standardised), as opposed to the US method where each phone in the house had to be wired properly for party line ringing?

Surely it was not to save the cost of a ringer capacitor in each phone?

-Bill

The bell wire was separated, with one capacitor in the master socket, so that the bell wire could be shunted during dialling, preventing bell tinkle.

The US parallel connection means there is always a conflict between the bell responding to weak ringing currents but not responding to transients from dial impulsing.

With tone dialling the problem does not arise, but in the 1980s when the modern Line Jack Unit socket system was introduced, tone dialling was a rarity in Britain.

Before the LJU sockets, phones were hard wired with all the bells in series, and the bell circuit was opened by the diall-off-normal contacts. The first, intermediate, and final telephones were all wired differently.

Where plug-in phones were used, jacks with a switching contact were used to maintain the series bell circuit when the plug was withdrawn. There would be one fixed telephone, or bellset, with a ringing capacitor, to indicate incoming call even if all phones were unplugged.

Australia used different jacks, but a similar series bell wiring system with switching contacts in the jacks.

dsk

Quote from: Phonesrfun on April 16, 2011, 08:06:58 PM
I never did understand why the UK and other Euopean countries systems were wired to split the ringer wire off at the main jack.  Was it so that in the olden days of party-line ringing, it could be wired properly at the main jack and then every phone in the house was standardized (standardised), as opposed to the US method where each phone in the house had to be wired properly for party line ringing?

Surely it was not to save the cost of a ringer capacitor in each phone?

-Bill
Most European countries use the same as the US system. In some period it was less important to have common standards, Germany has 60V ringing, UK has their splitted ringer circuit. Sweden has their special dial. Oslo and NZ has their reverse dial. France used to have "mother in law" receivers more or less as a standard.
Ringing frequencies use to be 25 Hz in 50 Hz mains areas, and 20 Hz in 60 Hz mains areas.
Still US telephones will work (speech and ringing) all over.

Norway tended to use extremely long lines at the country side, and pre WE 500 telephone circuits seems to cope better with these lines. 

Re filtering:
My experience from the modem times was separating ringer was important, a triac/diac filter was perfect.


dsk