Thank you for that view of the utilities cupboard. It is unfortunate that the service cables to each flat have been run so close to the three-phase mains supply. At least they cross at right-angles.
Moving on to the picture of the NTE5/A . . . or more specifically the IDCs and wires on the lower front removable face-plate. It looks to me as if the blue/white stripe, orange/white stripe and white/blue stripe wires are connected. Unfortunately, from that picture, I am uncertain of the IDCs to which those wires are connected.
Just a moment . . . Having now had a rummage in my grotto for a spare NTE5/A face-plate, I believe the wires are connected as follows:
- white/blue stripe wire to IDC2
- orange/white strip wire to IDC3
- blue/white strip wire to IDC5
Please confirm my assumption.
Now the good news. The lower front face-plate of the NTE5/A (and the wires connected there to) are "yours". They are the feed to the other socket in your office. So everything is looking good.
Your first task is to gently pull the orange/white stripe wire out of IDC3 and carefully tuck it away with the other unused wires from that cable into the backing box.
Your second task is to take the new LJ4F into your office, snip the cable tie holding the cable onto the existing socket and pull the two wires out of the IDCs. Trim off the ends of those two wires (just enough to remove the "used" bits) and with an insertion tool (hopefully you have one!) insert the white/blue stripe wire into IDC2 and the blue/white stripe wire into IDC5. Fix the cable to the strain relief with a cable tie and fit the socket into the backing box.
The third task is to return to the NTE5/A and temporarily re-fit the lower front face-plate. Test the telephone socket at the NTE5/A and the at the LJ4F in the office and confirm that both are working.
Your fourth and final task is to return to the NTE5/A, remove the lower front face-plate (you didn't fit the screws? . . . I did say temporarily, above
) and gently remove both wires from the lower front face-plate. Fit the SSFP (Service Specific Face Plate) to the NTE5/A and then, after trimming off the "used" bits, connect the white/blue stripe wire to IDC2 and the blue/white stripe wire to IDC5 of the SSFP. (The two IDCs to which that yellow arrow points in the illustration with your original post.) Now fit the lower front face-plate to the SSFP, using the longer screws that should have been provided.
The job is now done. Both telephone sockets are now filtered and you have an xDSL socket available in the office for your modem/router.
Please let me know if anything is not clear. It is far easier to do than it is to clearly explain.