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Table 8 shows the lost calls due to busy route, conflicting call on bothwayline, internal congestion and faults in the trunk exchange markers. The tableis based on the average of the period 9.30—10.30 a.m. for the first six monthsof 1956.Table 8Ma rkersoriginati ng trafficNumber0Markersincoming trafficNumber%OccupationsEstablished connectionsBusy routesOther lost calls4,7854,2734684410089.29.90.95.8735,3564526510091.27.71.1Specification of other lost callsConflicting callsInternal congestionFaults224180.40.10.41827200.30.50.3As shown by the table, the number of non-established connections in thebusy hour was roughly 10%, the main cause being 8—10% busy routes.As already mentioned, the service data given in this article are averagedata only. But it can be said that at the present time the exchanges are workingto the full satisfaction of subscribers, and there is no doubt that with carefulmaintenance the trouble rate should be low and the expenditure on maintenancecomparatively slight. Maintenance time must of course not be cutbelow the point at which constant satisfactory service can be provided. Onthe other hand, entirely trouble-free service should not be considered necessary,since the last per mille of faults would be very expensive to eliminate.8