Technical question - FAO BT/telecoms engineers

[greenstripe]

Hi.

 

I had a problem yesterday - I deal with tills and computers and was at a customer's shop yesterday. I went to install a broadband (ADSL) router on the BT line, but found that plugging a micro filter in to any telephone socket killed the phone line - no dial tone. I'm assuming that there's a problem with the phone wiring - I tried two different micro filters.

 

It is outside of my remit to touch any of their phone wiring - but is there anything obvious that would cause this? 

 

Telephone master socket appears to be original BT Master socket from ancient history and has a couple of home made looking extensions attached 

 

Normal telephones and old school 56k fax modem work fine

Edited 22 March, 2017 by greenstripe
Missed out a bit

[ashfan]

Don`t know if this is relevant but we recently switched to BT using one of their Smart Hub routers and their instructions say do not use a micro filter. the engineer didn`t fit one (we had our line moved, so a new installation basically) and everything works fine. 

[greenstripe]

New BT Master sockets have a micro filter built in (the ones with internet socket on top plate and telephone on bottom plate) so any telephones are already filtered.

 

I'm guessing either the wires are round the wrong way/damaged or damp somewhere, or there is simply too much wiring so there is not enough power in the phone circuit with the microilter attached 

 

 

 

[jjc]

You should be able to remove to outer faceplate on the BT master socket and under this should be the "direct connected" socket, you could try useing this. However if the extention wiring was not done correctly and is tapped in direct on the incomming pair this will be a problem. The incoming pair should connect to contact 2 and 5

 

John

[greenstripe]

5 hours ago, jjc said:

You should be able to remove to outer faceplate on the BT master socket and under this should be the "direct connected" socket, you could try useing this. However if the extention wiring was not done correctly and is tapped in direct on the incomming pair this will be a problem. The incoming pair should connect to contact 2 and 5

 

John

 

I did try connecting to to internal socket with the same results. There were 2 sets of wires coming from behind the socket directly to the faceplate with all six terminals connected same colours/terminals used (parallel):

 

1 orange-white

2 blue-white

3 green-white

4 white-orange

5 white-blue

6 white-green

 

Not really my place to touch their wiring, but I have grave misgivings about their technical support being able to solve the problems in a timely manor, which is going to affect a national rollout with this being the last shop of over 100 to be still on the old system. The shop in question is approximately 150 miles from me so not really something i can pop back to without proper arrangements

 

 

[Auric Goldfinger]

You'll need to talk to Briskodian Lee01 

 

 

 

Oh hang on, he's on a job at the moment  sat in a lay by having a cuppa

[@Lee]

2 minutes ago, Auric Goldfinger said:

You'll need to talk to Briskodian Lee01 

 

 

 

Oh hang on, he's on a job at the moment  sat in a lay by having a cuppa

Sorry mate, I'm sat in the van having a cuppa.

I don't touch internal stuff and if I do I only ever connect the external to the internal lead in to the Master socket (white Blue to White Blue on A & B of the socket). Never done an extension but, as mentioned, most stuff doesn't use a filter these days; that's usually for old VDSL IIRC.

[Auric Goldfinger]

23 minutes ago, Lee01 said:

Sorry mate, I'm sat in the van having a cuppa.

I don't touch internal stuff and if I do I only ever connect the external to the internal lead in to the Master socket (white Blue to White Blue on A & B of the socket). Never done an extension but, as mentioned, most stuff doesn't use a filter these days; that's usually for old VDSL IIRC.

 

Nice one, 

[@Lee]

35 minutes ago, Auric Goldfinger said:

 

Nice one, 

No, two sugars, ta

 

[VWD]

I'm talking old style master sockets ( NTE5), where external BT line goes to inside of socket, and is transferred to front via the plug/socket arrangement. Extensions come via the IDC connectors on the front plate ( or that's how it's designed to work) , but I've seen a lot of variations (and some TV /electrical firms don't seem to know this) on this. BT Master/ NTE is terminating point of BT line. ( Also called the NTTP) .

Personally, I never use more than one filter in my house , as you don't have to . I send line to PC, THEN filter off ADSL to PC, and then line to rest of premises/house.

In theory, there's an A & B leg to each line( normally, but not always wh/bl + bl/wh of cable, for internal cable, Or+WH for dropwire/ PR 1 of a UG cble), but in practice ,for extensions, if every socket follows the same colour code ,then there's no problem. Problems start when this pair is reversed, as it can affect ringing etc.

A master socket has a capacitor between pins 2 &3 . AC ,but not DC will pass through this. ringing is AC, and so passes from pin 2 to pin 3 , through the bell circuit and back to pin 5, preventing the bell from shorting out the line.

 

 

Edited 24 March, 2017 by VWD

[jonoj]

Did you use the SAME micro filter in all the sockets or multiple filters. If you have a faulty filter, then that may cause dial tone to be removed, especially if it all worked before, its possibly short circuit. 

 

The filters apply the filter part of the circuit to the telephone socket part, and the ADSL socket for the modem normally is exactly the same as the line coming in (the connection comes off before the filter for the phone line). So the ADSL/VDSL will work without filters but there is the possibility that noise from the unfiltered phone line would cause the line to resynchronise. 

 

The connection to your house is a pair of wires, and traditionally wire 3 would connect through to wire 2 through a capacitor. This is for old phones and new modern phones dont need this wire any more, but this in effect creates an unbalanced pair and acts as as antenna for noise if you have lots of extensions this can reduce the bandwidth as adsl/vdsl works most effectively with a balanced pair. Personally i disconnect wire 3 and see a small improvement and have never had a phone not ring because of this modification.

[VWD]

jonoj- that is one reason I use the old transmission maxim of separating the signals at the nearest point to where the HF signal needs to come off. The main source of degradation of a BB signal is a capacitor looping the HF path . My method ( and endorsed by a filter maker) consists of a two wire path to the PC, where ADSL is filtered off and the audio line is also filtered off .ADSL is sent to PC. Audio to rest of house wiring. in my house, I fit ONE filter at the master socket ,and supply the WIFI router from that. The phone side is sent to house wiring. same principle as sending 4.5KV over a submarine cable along with hf channels and separating at each repeater, or sending 1kv + 1000 calls down a co ax cable and separating power and hf at each roadside repeater .It is also used in the digital age ,with signals + power fed down a cable and separated at each regen