Abstract: A plate-type heat exchanger element for a plate-type air to air heat exchanger. The heat exchanger element comprises a heat exchange partition sheet and a spacer member comprising a corrugated mesh of expanded sheet metal. The corrugated mesh has an upstream side edge and a downstream side edge. The upstream side edge and the downstream side edge are folded over edges.

Abstract: Method of making a twisted conductor wire unit in which each wire of the pair is individually insulated. The twisted pair is provided with an outer extruded polymeric layer while a vacuum is applied to the pair at the extrusion position. The vacuum draws the polymeric layer down onto the pair and forces the insulated wires together along the length of the unit. The vacuum is insufficient to produce substantial longitudinal indentations in the polymer layer. This avoids spaces being provided between the insulated wires in the finished structure and provides a substantially constant distance between the wires to improve electrical and cross-talk characteristics.

Abstract: A telecommunications cable having a cable core in which each conductor is surrounded by an individual dual layer insulation of an inner layer of flame retardant polyolefin and an outer layer of fluorinated ethylene propylene. The cable is for plenum chamber usage in which smoke is to be minimized. Although the flame retardant polyolefin is a known smoke generating substance which does not satisfy plenum test smoke requirements, its use in this structure is entirely suitable for plenum chamber use because little or no smoke is actually generated as the outer layer protects the inner layer from combustion.