Abstract: A wire tensioning device having a guide for taking up an advancing wire having slack and a brake for applying a braking force to the guides. In a wire insulating system, a wire from a supply reel or spool is passed to a take-up reel or spool, through intervening components, which accumulate, tension and apply insulation to the advancing wire. The wire is first passed from the supply reel to an accumulating device in the form of a vertical accumulator or a flipper payout. From there it is passed through the device of the present invention having a plurality of rotatable sheaves or pulleys about which the advancing wire is trained. A braking force is applied to one of the sheaves by an air brake to apply a tensioning force. From the tensioning device, the wire is fed through an insulation-applying crosshead device and then on to a take-up reel or spool.