Manufacture of cable cores

A method of treating a stranded construction of a plurality of similar stranded together insulated conductors in a core for telecommunications cable comprising:

• having the core in a reeled condition with the core having two end portions accessibly positioned outside the reel;
• forming the conductors into two groups with the number of conductors in a first of the groups being substantially equal to that in the second of the groups;
• disposing the groups electrically in series with one another by electrically connecting the first and second groups together at one end of the core, electrically connecting the groups at the other end of the core, one to each of two terminals of opposite potential;
• heating the core with it in the reeled condition by passing an AC single phase current from said other end to said one end of the core, along the first group of conductors in one direction around the reel, into and along the second group of conductors in the opposite direction around the reel from said one end to said other end of the core, heat in the conductors flowing into the insulation to increase the temperature at the outer surface of the insulation;
• and periodically measuring the current and voltage applied to the conductors and from these measurements determining the resistance of the conductors to provide a measurement of the temperature of the conductors;
• and
• unreeling the stranded construction and passing the unreeled construction through a chamber containing a flowable core filling substance, the flowability of which increases with an increase in temperature, the filling substance being caused to flow into the interstices beween the insulated conductors to fill the core, the heated core retaining a higher than ambient temperature in the filling substance to assist its flowability.