| Network Termination Equipment (NTE) |
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| Line Jack Units (LJU) |
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LJU Master sockets are usually easily identifiable as the line jack unit will contain a ring capacitor, surge arrestor &
resistor.
To the right is a photo showing typical component layout of a master socket found in the home. Layout and colour of the circuit board may vary slightly depending upon date and manufacturer.
Connector pins are usually white IDC, which need a Krone insertion tool, but some older versions may have screw connectors.
Below are some photos of typical line jack units which may be found in the home.
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Further help with line jack identification.
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Faceplate - Front
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| Type |
Size |
Phone Jacks
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Phone Lines
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| LJU1 |
55mm x 55mm x
29mm |
1
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1
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| LJU2 |
68mm x 68mm x
29mm |
1
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1
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| LJU3 |
86mm x 86mm |
1
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1
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| LJU4 |
86mm x 86mm |
2
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2
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| LJU5 |
86mm x 86mm |
2
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1
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Components
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Series
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Capacitor
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Surge Arrestor
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Resistor
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Terminal
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Type |
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/1
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Yes
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Yes
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Yes
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IDC
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Master |
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/2
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Yes
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-
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-
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IDC
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Master PABX |
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/3
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-
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-
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-
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IDC
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Secondary |
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/4
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Yes
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Yes
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Yes
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Screw
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Master |
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/5
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Yes
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-
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-
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Screw
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Master PABX |
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/6
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-
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-
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Screw
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Secondary |
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| Block Terminal Connectors |
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BT connectors (Block Terminal)
Used by BT to connect standard telephony wiring.
These are the property of BT and should not be tampered with. |
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| Most commonly seen to connect the drop wire to internal cable and are often found in the loft or other point of entry to a building. |
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BT77A
3 pair IDC to
3 pair IDC |
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BT77B
3 pair screw to
3 pair screw |
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BT78A
4 pair IDC to
4 pair IDC |
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BT80A
3 wire IDC to
drop wire |
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BT92A
BT Redcare Alarm |
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BT92A
Internal.
Use caution if checking your telephone wiring to ensure you don't inadvertently set off the alarm |
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BT80A RF2
3 wire IDC to screw
with 2 x inductors
Can cause problems with adsl. If you have one of these contact your ISP to arrange an RF3 to be fitted free by Openreach. |
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BT80A RF3
3 wire IDC to screw
with 2 x inductors
Used to help filter RF interference
for voice |
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| Telephone Wire Colour codes |
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| Pair # |
a-wire |
b-wire |
Pair # |
a-wire |
b-wire |
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| 1 |
WHITE-blue |
BLUE-white |
16 |
YELLOW-blue |
BLUE-yellow |
| 2 |
WHITE-orange |
ORANGE-white |
17 |
YELLOW-orange |
ORANGE-yellow |
| 3 |
WHITE-green |
GREEN-white |
18 |
YELLOW-green |
GREEN-yellow |
| 4 |
WHITE-brown |
BROWN-white |
19 |
YELLOW-brown |
BROWN-yellow |
| 5 |
WHITE-grey |
GREY-white |
20 |
YELLOW-grey |
GREY-yellow |
| 6 |
RED-blue |
BLUE-red |
21 |
VIOLET-blue |
BLUE-violet |
| 7 |
RED-orange |
ORANGE-red |
22 |
VIOLET-orange |
ORANGE-violet |
| 8 |
RED-green |
GREEN-red |
23 |
VIOLET-green |
GREEN-violet |
| 9 |
RED-brown |
BROWN-red |
24 |
VIOLET-brown |
BROWN-violet |
| 10 |
RED-grey |
GREY-red |
25 |
VIOLET-grey |
GREY-violet |
| 11 |
BLACK-blue |
BLUE-black |
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| 12 |
BLACK-orange |
ORANGE-black |
| 13 |
BLACK-green |
GREEN-black |
| 14 |
BLACK-brown |
BROWN-black |
| 15 |
BLACK-grey |
GREY-black |
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| External NTE |
With effect from Dec 2008, BT have started installing External NTEs on new build properties. These new NTE housing boxes can terminate up to 2 x copper pairs.
The box will be located on the exterior of the premises allowing BT Openreach Engineers easy access for testing etc and are clearly marked "Wiring and equipment from this point belongs to the property owner. Where Openreach attend for a reported fault and determine that the fault is beyond this point the visit and any work will be chargeable." |
External NTE
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Inside the grey NTE is a red tamper proof unit where the copper pair terminates and are connected to the box by an IDC labeled A and B.
The box is also said to contain a filter to help prevent electrical interference.
Entry point to the customer premises is via a cable that passes through the rear of the box which connects to IDC terminals labeled 2, 3 & 5. The orange ringwire is not connected in order to reduce interference on adsl enabled lines. |
Inside the External NTE box
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The External NTE unit contains a yellow plug which can be removed to disconnect the customer owned wiring, when testing by an Openreach Engineer.
BT appear to be connecting these new units internally to LJU's (non NTE5 sockets) which unfortunately means that there is no internal test socket for the customer. |
 
BT yellow plug & test socket
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Thanks to Zen Tech - A Eldridge for the External NTE photos
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More information on phones and sockets can be found at Telephones UK
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