How to Terminate?

Platted cords were, as you know too well, cut off at the wall box by the 1000s, leaving collectors with a problem. Leads are valuable but how do you effect a good repair? Crimps...waste of time, solder...won't wet the copper.

If you have a copy, look at page 170 of J Atkinson, Telephony Vol 1, by Pitman & Sons published 1948 last reprinted 1964, which shows the ‘make up’ of a typical lead. This gives some clue, together with an inspection of an intact lead, of how to make a termination.

It may seem complex from my description, but with practice it takes about 20minutes to re-terminate a wrecked three core lead. I can say that having terminated not less than 250 leads this way, it most definitely works and the failure rate is about 1 in 100. Clearly, the finished job can never match the GPO termination, which was machine done, but it is close and as I state above, it does work. 

Tools and Equipment Needed

  • Small soldering iron, say 20-25watt & stand.

  • 0.75mm2 multi-strand copper single core wire, you need at least 20-25 strands, they need to be a little thicker than human hair.

  • Rosin cored solder, usually sold in 25gm packs.

  • Reels of cotton: red, green, white, brown, ivory.

  • Electrical side cutters.

  • Electrical cable strippers.

  • Sharp craft knife.

  • Heat resistant mat.

  • Continuity meter/electrical tester. 

Note! My description assumes that a brown lead is being re-terminated.

First Step:
Check your damaged lead for continuity as there is little point in ‘fixing’ a dud lead, if OK unwind enough of the three/four cores at the damaged end, say about 75mm, cut off the blank filler core, leaving the three 75mm long conductor cores.

Then, to stop everything coming undone, hold the three cores together at the point were the plait stops and wrap about 50-100 turns of brown cotton around to hold it all together. Then with 3 or 4 half hitch knots tie off your wrapping. You should now have a smooth wrap of brown cotton at the end of the plait, with three 75mm tatty ends! To finish off the wrapping and to make sure it does not come undone use melted beeswax (used on the originals, applied by brush), or Evostic, smelly but effective!

Second Step:
Using a sharp craft knife take one of the three tatty ends and cut about 6-10mm of the brown outer cotton cording and inner silk braiding away. You will then see the inner copper tinsels, each of which is wrapped in silk strands. It does not matter if there are still silk strands mixed with the exposed copper tinsels.

Strip about 50mm of the 0.75mm2 copper cable using the strippers, but leave the 20-25 exposed conductor strands attached to the cable. The technique is ‘wire wrapping’, bend about 8-10 strands of copper on the cable away from the others. Then select your tatty end and place the 8-10 strands against the exposed tinsels/silk strands and wrap the copper cable strands around them about 6-8 times.

Very carefully place your wrapping on a heat resistant mat ready for soldering. The secret of soldering is a clean hot iron, which is already lightly tinned. Place the iron against the wrapping at the same time as the solder, capillary action will pull solder onto and into the wrapping. Don’t worry about bits of silk, they burn away and a good copper/copper contact is made.

Third Step:
You should now have a lead with one soldered end attached to you reel of cable. Cut the 8-10 strands free of the reel and put the reel to one side. Twist the cable strands so as to form a loop, then wrap them back over your freshly soldered wrapping. Place on the mat and then solder the loop and second wrapping to the first. Test for continuity, then select red/white or green cotton and wrap around the brown outer cotton and inner silk braiding to colour code the end and stop everything from fraying. Don’t forget to half hitch knot and glue/wax to keep everything in place. Repeat steps 2 and 3 for the second and third cores.

By Peter Bailey

BACK Home page BT/GPO Telephones Search the Site Glossary of Telecom Terminology Quick Find All Telephone Systems

Last revised: October 30, 2022