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References 1. C.C.T.T. Illrd Plenary Assembly. Blue; Book, Vol VII—Telegraph Switching, Geneva 1964. 2. MCKINNON, R. K.: Automatization of the Australian Telex Network — Part I. Telecomm J. Aust. 7.5(1965): 2, pp. 108—115. 3. MCKINNON, R. K., CRANE, N. R. & KROL, J. R.: Automatisation of the Australian Telex Network — Part II. Telecomm. J. Aust. 75(1965): 3, pp, 308—228. 4. ROSSBERG, E. A. & KORTA, H. E.: Teleprinter Switching. Nev York 1959. 32
Corrugated Plastic Conduit Ducts G. ABERG, TELEFONAKTIEBOLAGET LM ERICSSON, STOCKHOLM UDC 621.315.616 621.315.671 LMF 823 The corrugation of plastic ducts increases their radial rigidity. The L M Ericsson Network Department has developed a corrugating machine which produces from thin-walled plain ducts a corrugated duct with the same (or better) mechanical properties as a non-corrugated duct with walls 3^f times as thick. Non-corrugated plastic ducts are being increasingly used in outdoor conduits. They have many advantages: low weight, which reduces the freight and handling costs, no risk of corrosion of lead-sheathed cables, waterproof conduit, a certain flexibility, reduced friction, which allows longer distances between manholes, etc. These ducts, however, must have a fairly thick wall, which makes their price high. Corrugation permits the use of thinner-walled ducts and so reduces the price. Non-Corrugated Plastic Ducts Ordinary non-corrugated plastic tubing, 6 m in length, is a general commercial commodity in most industrial and certain developing countries. The diameter of the tubing varies. There are two reasons for this. • Different diameters of duct are required in different parts of a local cable network. Near the exchange large-diameter ducts are required to accommodate multipair cables. This tendency will be accentuated through the use of light cables and, to a still greater extent, if copper conductors are replaced by aluminium. On the outskirts of the network and for secondary cable runs, on the other hand, a smaller duct diameter is sufficient. • The second reason is that, with different diameters of duct, the ducts can be telescoped into one another and so form a more convenient transport package. This is an important advantage when the ducts have to be transported a long distance from the place of manufacture to the site of corrugation and installation. The freight cost for ducts of a single dimension is unreasonably high. A set of ducts NTB 30101 contains nine ducts telescoped into one another. Their outside diameter varies between 70 and 110 mm in intervals of 5 mm. 33
Page 1: 1 1968
Page 4 and 5: Stored Program Controlled Telephone
Page 6 and 7: Signalling in L M Ericsson Telex Sy
Page 8 and 9: On physical subscriber lines other
Page 10 and 11: In a new Recommendation U 11, CCITT
Page 12 and 13: Automatic Tripping of B Subscriber'
Page 14 and 15: egister in ARM selects a new circui
Page 16 and 17: show the signalling both for single
Page 18 and 19: Fig. 11 gnalling for setting up a c
Page 20 and 21: In this case, after receipt of the
Page 22 and 23: Similar intervvorking exists with t
Page 24 and 25: The capital cost of the telex syste
Page 26 and 27: Fig. 1 Traffic distribution by dist
Page 28 and 29: Fig-3 Charging principles Zone char
Page 30 and 31: Transmission Considerations The obj
Page 32 and 33: A variety of special subscriber mar
Page 34 and 35: to be tripped. The calling subscrib
Page 38 and 39: Corrugating Machine The aim in the
Page 40 and 41: Laying The corrugated duct may have
Page 42 and 43: New Factory Opened at Ostersund L M
Page 44 and 45: Dirivox and Centrum in the Soviet U
Page 46: The Ericsson Group Associated and c

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