age 3. Moulded strip divided and centre conductor introduced. in the dielectric support. Further disturbances can arise during factory operations prior to and during the laying up of a multipair Stage 4. Two halves heat-consolidated together around centre cable, for example, roughness on an intermediate process drum. conductor, forming single tube with integral spacing discs and two The resultant reflections can be assessed by pulse echo testing and longitudinal fins. swept frequency reflectometer testing as a routine factory test and Stage 5. Fins removed to give insulated conductors. the product quality controlled to system requirements. Two soft steel tapes of thickness 0.1mm are lapped around the outer copper, in opposite directions in such a manner as to cross each other at right angles. The inner tape has a nominal 5% gap between 15.3.3.3 Attenuation turns, and the outer which is wider but applied at the same lay length has a nominal 15% overlap. Two thickness of insulating tape, with The attenuation coefficient is specified at 1MHz in dB/km. To a colour coding are then applied. The novel method of steel tape close approximation the loss at other frequencies is inversely pro- application ensures high crosstalk immunity between coaxial pairs portional to the square root of the frequency. For example, the loss at low frequencies and the whole manufacturing process can be at 9MHz is three times the loss at 1MHz. More exact formulae are controlled to ensure a consistent product. provided for a 1.2/4.4mm and 2.6/9.5mm Coaxial Pair, in Section 15/8 Telecommunication cables 15.3.4, which include a constant and an f term. Alternatively the A commonly used technique is to multiplex many information consistency of product is such that manufacturers can provide channels into a broadband spectrum extending up to 450MHz on a measured data on which the equalisation of analogue systems can single coaxial tube. Similar transmission equipment to that used on be based. multichannel cable TV systems can then be employed. Howe