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the keyset type control panel. TheCTC office will also have a traingraph.The Doboj-Zenica plant will becompleted in three stages and be fullyinstalled by 1960.C.T.C. for Jugoslavian RailwaysThe Jugoslavian Railways havedecided to install modern interlockingsystems and centralized traffic control(CTC) on the very heavily traffickedDoboj-Zenica section comprisingsome 100 kilometres of thesingle track line between Brod andSarajevo. L M Ericssons Signalaktiebolaghas received an order for theequipment and will also supervise thework of installation.The Doboj-Zenica section hastwelve stations, each with three orfour tracks. The traffic is very heavy,and the present capacity of the lineis inadequate. The capacity will beincreased, however, by the introductionof signalling equipment andCTC, which will render the sectioncapable of carrying the heavier trafficthat is anticipated within the nextfew years.All stations will have relay interlockingplants, but only the four largestexchanges will be equipped withlocal control panels that can be operatedwhen the stations are disconnectedfrom the CTC system. TheCTC office will be located at Doboj,and all stations will normally be controlledfrom it.Some ten road crossings will beprotected by lifting gates and signalsfor automatic control by trains.The CTC system will be of L MEricsson's standard type with the illuminatedtrack diagram separate fromEricsson TechnicsEricsson Technics No. 2, 1956, hasrecently appeared. An article by ProfessorC G Aurell of the ChalmersUniversity of Technology, Gothenburg,entitled "The Equivalent TransmissionLine of a Linear Four-TerminalNetwork. Calculations with Cascade-ConnectedFour-Terminal Networks",describes a systematic procedurefor the calculation of impedancesand powers in cascade-connected fourterminalnetworks. The concept"equivalent transmission line" is extendedto apply also to non-symmetricaland non-reciprocal four-terminalnetworks. The article "New Types ofSections for Zig-Zag Filters" by ProfessorT Laurent, of the StockholmInstitute of Technology, presents newtypes of band-pass sections named"zig-zig" and "zag-zag" sectionswhich can be introduced into a zigzagfilter ladder without producingreflection. This provides full freedomin the choice of attenuation peaks ina filter ladder of this kind.Finally, an article by H Hiiggblomand S Tomner of AB Svenska Elektronror,Stockholm, "Developmentsof the Strophotron", describes thetheoretical and experimental workdone on the development of strophotronoscillators within the frequencyrange 1,000-5,000 Mc/s.On the iooth Anniversary of the SwedishState Railways on December I, 1956,Messrs. H Thorelli, H Lindberg, H Insulanderand A Westling presented adeed of gift for 25,000 kronor fromthe Ericsson group to Erik Upmark,head of S.S.R. It is proposed that thissum shall be used for scholarships toS.S.R. staff for travel within Europe.32$