How to splice telephone wire

The need to splice telephone wire arises when problems with the original wiring occur. Open circuits can occur in the original wiring that was installed while the home was being built and disrupt telephone service to parts of the house. In cases like this, it's easier and quicker to splice in a new section of wire to bridge the bad section than it is to try to locate where the open circuit is located inside the finished walls. Splicing is also required when you want to extend old wiring.

Preliminary tasks

Adjust the bite of the adjustable wire strippers. Adjust the depth of cut on the wire strippers so that they just break through the thickness of the insulation without cutting into the copper conductor itself. Using a small screwdriver, loosen the locking screw on the wire stripper and, using a scrap piece of wire, find a setting that cuts cleanly through the wire's insulation without scoring the conductor. Telephone station wire, a solid copper conductor, is fragile and easily damaged during the splicing operation. Scoring the circumference of the conductor with the wire strippers while removing the insulation increases the conductor's resistance and weakens the wire physically. Once finished, lock the screw tightly in place.

Heat your soldering iron and clean the tip by wiping it on the wet soldering sponge.

'Tin' the soldering iron tip by applying a fresh coating of Rosin Core solder to it. A properly tinned tip will appear a bright silver colour. A properly cleaned and tinned soldering iron tip is the first step in making good solder joints.

Solderless butt splices

Remove 1.2 cm (1/2 inch) of insulation from the ends of the two wires to be spliced together using the wire strippers.

Insert one of the stripped conductors in each end of the solderless butt splice connector. Never insert more than one conductor in each end because they won't crimp properly and a bad electrical connection will result. A good electrical connection begins with a solid mechanical connection.

Crimp the connector down firmly on the stripped wire using the proper colour-coded slot on the crimping tool.

Soldered splices

Remove 2.5 cm (1 inch) of insulation from the ends of the two wires to be spliced together using the wire strippers.

Cut a piece of heat shrink tubing 3.7 cm (1 1/2 inches) long and slip it over one of the wires to be spliced together.

Hold the two stripped ends so they cross each other at a 45-degree angle and then wrap the two projecting ends tightly around its opposite conductor in opposite directions.

Apply the hot soldering iron tip to the underside of the splice while applying the solder to the top side. Capillary action will suck the molten solder around and through the splice.

Slip the heat shrink tubing over the soldered splice and shrink tightly down on the splice by applying hot air from the hot air gun.

Self-stripping solderless splices

Select the proper size connector for the number of wires to be spliced together. These connectors come in 2, 4, 6, and 8 conductor sizes.

Slip the conductors through the connector so they project slightly from the other side.

Crimp down firmly using the crimping tool. The wire insulation is pierced and the connections are made as the connector is crimped in place.

Things You'll Need

  • Diagonal pliers/wire cutters
  • Adjustable wire strippers
  • Small, flat-blade screwdriver
  • 35-watt soldering iron
  • Soldering sponge
  • Rosin Core solder
  • Hot air gun
  • Heat shrink tubing
  • Solderless butt splices
  • Self-stripping crimp-on telephone/alarm connectors
  • Crimping tool
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About the Author

Based in Colorado Springs, Colo., Jerry Walch has been writing articles for the DIY market since 1974. His work has appeared in “Family Handyman” magazine, “Popular Science,” "Popular Mechanics," “Handy” and other publications. Walch spent 40 years working in the electrical trades and holds an Associate of Applied Science in applied electrical engineering technology from Alvin Junior College.