Bt Connections / Telephone Extension / Phone Fault Bt Info

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If you have too many master sockets, the phone won't ring. It's all about Ringer Equivalence Numbers (REN). Most telephone handsets have a REN of 1, some old fax machines are 1.5 or even 2. BT guarantee a REN of 4, meaning you can have 4 phones plugged in and they'll all ring. Each master socket is REN1. So if you have 4 master sockets, you can have 0 phones ringing.

When wiring them up, connect BLUE/white to 2, WHITE/blue to 5, ORANGE/white to 3, and WHITE/orange to 4. 4 isn't actually used, but it should be connected to balance the cable, or you may find you have problems with broadband, particularly if you live a long way from the exchange.

Although the line only uses 2 and 5, and 3 for the ringer, 4 must be connected to balance the cable. It's best to connect all six wires to be certain of no conflicts.

Colours (for cable post 1985ish)

1 = GREEN/white ring

2 = BLUE/white ring

3 = ORANGE/white ring

4 = WHITE/orange ring

5 = WHITE/blue ring

6 = WHITE/green ring

Older cables

2 = Blue.

3 = Green.

4 = Brown.

5 = Orange.

Fault Finding

No ringing -

Terminal 3 disconnected

Phone ringing continuously -

Terminals 2 and 5 swapped (2 at one socket connected to 5 on another and vice versa)

Very poor speech quality, possibly poor bell. -

Terminal 3 and 2 or 3 and 5 transposed

Ringing but no speech (or very poor speech) and can't dial out. -

Wire between terminals 2 or 5 broken.

BT Dropwire comes with 2 pairs of cores.

Pair 1 is WHITE & ORANGE

Pair 2 is BLACK & GREEN

Only 1 pair is used for a single phone line and this is usually Pair 1, but not always!

Pair 1

WHITE = White/Blue Bands = Terminal 5

ORANGE = Blue/White Bands = Terminal 2

Pair 2

BLACK = White/Orange Bands = Terminal 4

GREEN = Orange/White Bands = Terminal 3

BT line voltage is -48v DC wrt earth across pins 2 and 5, supplied at 40mA. Ringing voltage is 70v RMS AC superimposed on the DC line.

 

sellers

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Just thought I'd nudge this up, very good info. Thanks.

 
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Very useful info. I have worked in telephone exchanges and we take that -48VDC a bit for granted. I have seen massive rectifiers, battery stacks and back up gennies all so we can have our -48V on our phone sockets. I'm not quite sure why he is saying if you use 4 x master sockets you can have 0 phones ringing?

 

sellers

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I'm going to look at a dodgy phone line tomorrow so it helps a lot, not really delved too far into phones before. There was a thread with a decent diagram in of how they should be wired not so long ago, but i can't find it?? Patch ;) Pray

 

Theorysparky

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Sellers

First thing to do is remove front cover from the master socket and plug in there..........using a known good phone that you have (not a walk around)

if that works fine then look at the front cover to see how many extensions they have wired in..

look for the cable runs.......gripper rods are a problem

telephone extension leads are a good source of faults

then of course there is my favourite.......socket smashed by hoover..

other than that we could do with more info

 
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I kept getting a fault at my mums house, phone would stop working. Checked plug in adaptor pins burnt, checked phone socket, pins burnt.

changed BT outlet, 3 months later same scenario, changed again, a few months later same again! noticed the screw holding the pattress on to the wall was corroded indicating damp. re located the box and fitted another BT - everything fine now. Strange or what?

 
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an old type wired phone is useful for checking stuff like this. also try and get your test phone without the ringer stuff built in, or if you have no signal at 3, the phone will extract the rings its-self from 2&5, so a fault may no show

 

sellers

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well as for extra info, the customer rang saying the line is very distorted and crackly and will cut off randomly.

 

Theorysparky

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when u go there listen to the fault before you do anything

check all connections then listen

if it is still there remove one extension at a time you will soon find it

beware of the walk about phones,,,if they are near microwaves tvs etc.. you will get distortion

let us know how you get on

 

sellers

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if it is still there remove one extension at a time you will soon find it
what do you mean by this? plug phone into master socket, then remove the extensions from the circuit? Its only a 1bed flat so can't imagine many if any extensions.

 

Theorysparky

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what do you mean by this? plug phone into master socket, then remove the extensions from the circuit? Its only a 1bed flat so can't imagine many if any extensions.
could have told us that earlier !!!!!! ;)

in that case matey peeps

my money is on the phone !!!!!

 

sellers

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well, the bloke says he's changed the phone, and rang bt for a connection check. It may have one extension. Just going to have to take a peak at it.

 
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Blimey!

someones been routing around the forum archives,

right at the back of the loft underneath the Christmas tree by the looks of it...

to dig this one out....

Even before I joined :eek: :^O:(

However not one to put a damp squib on things..

BUT there are a few inaccuracies in this post...

(said the bloke wot originally had an apprenticeship training in phones and got BTEC & HNC in Telecommunication Engineering!)

If you have too many master sockets, the phone won't ring. It's all about Ringer Equivalence Numbers (REN). Most telephone handsets have a REN of 1, some old fax machines are 1.5 or even 2. BT guarantee a REN of 4, meaning you can have 4 phones plugged in and they'll all ring. Each master socket is REN1. So if you have 4 master sockets, you can have 0 phones ringing.
MASTER SOCKETS:

The master socket contains the 'Bell capacitor' & the lightning surge protection & a resistor.

You only have ONE master socket per line.

NEVER two or more.

SECONDARY SOCKETS:

Secondary sockets do NOT have a bell capacitor or lightning surge protection.

You can have as many secondary sockets as you want on one line.. (No limit)

A master socket can be converted to a secondary socket by simply sniping out the three components on the rear of the PCB.

REN4:

As said this is the typical max number of phones that BT suggest their line equipment can ring at the furthest extremities from the telephone exchange... However If nearer to the exchange then higher REN's (more phone's) would work.

BUT...

The REN predominantly relates to the old-type of telephones with traditional bell's & mechanical armatures to ring em connected back to the third wire via the bell capacitor in the master socket, Most modern electronic base telephones & hands-free base stations Do NOT use the bell wire.. They pick up the ring straight of the main line pair. & thus draw minimal current from the line and REN value has negligible impact.. so could happily stick 4 or more modern phones & they will still work!

When wiring them up' date=' connect BLUE/white to 2, WHITE/blue to 5, ORANGE/white to 3, and WHITE/orange to 4. 4 isn't actually used, but it should be connected to balance the cable, or you may find you have problems with broadband, particularly if you live a long way from the exchange.

Although the line only uses 2 and 5, and 3 for the ringer, 4 must be connected to balance the cable. It's best to connect all six wires to be certain of no conflicts.
Terminal 4:

Quick bit of history;

not so many years back, In the days of dial telephones, your average factory / office / small business, had a receptionist who answered the phone and put calls though to various staff on the extensions using the internal PABX / PBX phone system.

If staff wanted to contact their receptionist (telephone operator) or put a call on hold whilst keeping the customer still on the line..

they pressed the 'Hold' or 'Recall' button on the phone...

This button used the wire connected to terminal 4 to signal the operator or internal phone system to keep the call on hold whist another call was made!

Again as modern electronics and Multi-frequency (tone) dialling has taken over from traditional Pulse (Loop disconnect) dialling we can now use codes and tones with other fancy buttons such as the star '*' and hash '#' keys to do the old functions of the hold / recall button.

and either way the hold to contact the receptionist was never needed on a domestic line anyway..

So Terminal '4' not needed.. makes no difference if it is left off or connected.

It will have NO detrimental affect on the performance of the domestic phone line, and it is most definitely NOT needed to balance anything up!

Colours (for cable post 1985ish)

1 = GREEN/white ring

2 = BLUE/white ring

3 = ORANGE/white ring

4 = WHITE/orange ring

5 = WHITE/blue ring

6 = WHITE/green ring

Older cables

2 = Blue.

3 = Green.

4 = Brown.

5 = Orange.

Fault Finding

No ringing -

Terminal 3 disconnected

Phone ringing continuously -

Terminals 2 and 5 swapped (2 at one socket connected to 5 on another and vice versa)

Very poor speech quality' date=' possibly poor bell. - [/b']

Terminal 3 and 2 or 3 and 5 transposed

Ringing but no speech (or very poor speech) and can't dial out. -

Wire between terminals 2 or 5 broken.

BT Dropwire comes with 2 pairs of cores.

Pair 1 is WHITE & ORANGE

Pair 2 is BLACK & GREEN

Only 1 pair is used for a single phone line and this is usually Pair 1, but not always!

Pair 1

WHITE = White/Blue Bands = Terminal 5

ORANGE = Blue/White Bands = Terminal 2

Pair 2

BLACK = White/Orange Bands = Terminal 4

GREEN = Orange/White Bands = Terminal 3

BT line voltage is -48v DC wrt earth across pins 2 and 5, supplied at 40mA. Ringing voltage is 70v RMS AC superimposed on the DC line.
well we always called it and refer to it in our exams.. as 50vDC & 80v ringing! ?:| :D

However there were quite literally banks of 1.5v cells making a 48v battery to keep thing running!

;)

 
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Apache's mislay telephone tip:

if someone rings you by accident with their mobile phone in their pocket and ties up your line there is an easy way to clear it. Pick up the phone, press recall you will get a dial tone. Hang up note the phone will ring do not answer it. Let it ring until it stops and then pick up the handset - your line is now clear!

This happens about once a month on our emergency line!

:D

 

sellers

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SL where do you learn this stuff???

went today. The phone line sounded ok. its just one master socket in the whole property. 2 cables coming in, blue/white and white/blue going to A and B on the master.

its a house converted into 2 flats. traced the bt cable outside and it all looks ok. didn't get a chance to look in the BT box, need my extension ladders. Looks like 1 cable coming from the pole into the box and seperating 1 for up flat and 1 for down flat. Gonna try a new master socket (are these known to fail) and get the ladders out to inspect around and inside the box.

 
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SL where do you learn this stuff???Did a 4 year telecommunications apprenticeship.. straight from school ages 16!!Blushing:D

went today. The phone line sounded ok. its just one master socket in the whole property. 2 cables coming in, blue/white and white/blue going to A and B on the master.

its a house converted into 2 flats. traced the bt cable outside and it all looks ok. didn't get a chance to look in the BT box, need my extension ladders. Looks like 1 cable coming from the pole into the box and seperating 1 for up flat and 1 for down flat. Gonna try a new master socket (are these known to fail) and get the ladders out to inspect around and inside the box.
phone line sounded OK.. it probably is ok then!

Did you stick your meter across the line? should have approx 50v DC

Sockets can go faulty..

double check the springy contacts inside the socket are not bent?

Are they using one of those adaptor plug in adaptor thingy's If yes remove it to prove the line!

Have you proved the telephone itself?

e.g

the physical flex from phone to telephone sockets can become damaged..

open circuit or intermittent broken conductor in flex

Same again with flex between handset & telephone

wiggle the flexes about see if phone cuts off or similar?

 
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Trailer boyo:

r.e. the "1 master socket" quote......I`se got 2!

When we refitted the study, a few years back, I had problems with a couple of the cores of my :eek:ops 4 core alarm cable :eek:ops , which feeds from my downstairs master skt.

So....I used two cores, and fitted a second master upstairs. Just as well, as my all-in-one with fax swears blind it "MUST be connected to a MASTER socket".

Don`t get much in the way of issues. If I answer the phone upstairs, the downstairs phone keeps ringing for a bit........But the old one didn`t!

 
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