Abstract: A polymeric tube is extruded; one or more strands are wrapped around the tube, the strands having a polymeric core and a high strength helical fiber cover; a second tube extruded thereon; at least one of the tubes is cross linked; subsequently the composite tube wall is heated, expanded and cooled in the expanded state; the tube may be cut longitudinally before or after the heating/cooling.

Abstract: A process is disclosed for the transmission of data between subscribers of a public dial telephone system in which at least a telephone, a data modem having a tone transmitter and a tone receiver, and a data device are connected to the dial telephone system. The data modem is equipped with a circuit for ringing voltage detection with bridging of ringing pauses. For transmission of a data answering tone and, if applicable, for selection of a channel position, in the case of manual operation, after operation of a data key, a distinction between the `called` state and `calling` state is made according to whether, at the start of loop current, a ringing voltage was detected by the data modem or not.

Abstract: Two concentric corrugated metal tubes have a space therebetween in which there is arranged a superinsulation layer. Between the inner tube and the superinsulation layer there is located a helical spacer to ensure an annular channel to facilitate the evacuation of the space between the corrugated tubes. The spacer is formed of interlaced strands to reduce heat conduction therethrough.