An insulated conductor (20) for use in a communication cable which includes a filling material (30) includes a copper conductor (25) and a composite insulation system (27) comprising two concentric layers of insulation. An inner foam layer (28) of the insulation comprises a cellular plastic material...http://www.google.es/patents/US5270486?utm_source=gb-gplus-sharePatente US5270486 - Metallic transmission medium disposed in stabilized plastic insulation
Metallic transmission medium disposed in stabilized plastic insulation
