1. - ericssonhistory.com

'Fig. 3 x 8014The Aarhus Syd exchangemethod employed instead is test calls, which were formerly made by operatorsbut are now performed by Ericsson's traffic route tester. Owing to the rotaryoccupation of the switching devices, an excellent survey of how the exchangesare working, and of their condition, is obtained by calling test numbers in thevarious thousands groups.Table 2 shows the result of some 50,000 test calls made in the first sixmonths of 1956 between 32 local numbers in the 32 thousands groups of theAarhus local exchanges. The calls were distributed among the exchangesaccording to their size.Table 2RouteNumbertest callsFaults andcongestion(quant.)Faults andcongestion(in %)Centrum, internalSuburban, internalCentrum—suburbanSuburban—CentrumSuburban—suburban20,0305,8509,4258,5756,000194141690.090.070.150 190.1549,880620.12The percentage of faults, including congestion, averages about 0.1 %. Thelargest percentage of faults is on inter-suburban exchange traffic. The reasonstor this are that congestion is calculated to be 0.5 % on junction circuitsas against 0.2 % in the switching stages, and also that more equipment iscalled into use. However, the fault percentage is so low that, including congestion,it is below the congestion specified in the tender.Faults found in automatic tests, as well as service complaints, are recordedon trouble cards and detailed trouble reports. As far as possible the faultsare traced and cleared. The number of faults and their nature are set out intables 3 and 4, covering the first six months of 1956. During that perioda total of 421 cards were dealt with at Centrum, and 166 cards at the suburbanexchanges. Of the faults reported at Centrum, 271 were cleared, while150 remained untraced. The corresponding figures for the suburban exchangeswere 127 and 39.4