. The Bell System technical journal . temperatures were measured atfour places along the 15-mile length of cable. From these tests theaverage 1000 cycle attenuation at 62° F. was found to be db per * See Irregularities in Loaded Telephone Circuits, George Crisson, Bell SystemTechnical Journal, October 1925. THE TORONTO-BARRIE TOLL CABLE 599 mile. In Fig. 6 is shown the mean of the attenuations of three pairsplotted against frequency. On one pair the measurements were madeat frequencies up to 6500 cycles, from which cut-off was determined totake place at 4000 cycles. Assuming a 60-mile cir
. The Bell System technical journal . temperatures were measured atfour places along the 15-mile length of cable. From these tests theaverage 1000 cycle attenuation at 62° F. was found to be db per * See Irregularities in Loaded Telephone Circuits, George Crisson, Bell SystemTechnical Journal, October 1925. THE TORONTO-BARRIE TOLL CABLE 599 mile. In Fig. 6 is shown the mean of the attenuations of three pairsplotted against frequency. On one pair the measurements were madeat frequencies up to 6500 cycles, from which cut-off was determined totake place at 4000 cycles. Assuming a 60-mile circuit, the frequencyat which the attenuation is about 10 db greater than 1000 cycles, isabout 3500 cycles. Before the return loss tests were made, impedance-frequency mea-surements were taken on two of the balancing networks for each of thethree adjustments provided, and on a representative number of cablepairs, to determine the optimum network adjustment. The resistancecomponent of the impedance for one of the networks and one cable. 500 600 600 1000 1500 2000 FREQUENCY IN CYCLES PER SECOND 4000 5000 Fig. 6—Attenuation-frequency characteristic; mean of measurements on three pairs. pair is shown in Fig. 7 (the two networks were found to be identical).From these tests the optimum network adjustment was determined tobe that corresponding to a cable capacitance of mfd per mile,which adjustment was then used for the return loss measurements. As it was desired to obtain the singing point to be expected underoperating conditions, the return loss measurements were made withthe building-out condenser on the return loss set adjusted for optimumreturn loss at 2600, 2700 and 2800 cycles. The results of thesemeasurements are given in Fig. 8 for comparison with the computedcurve ^ mentioned previously. The improvement at the higherfrequencies of the actual over the computed values is due almostentirely to the method employed in making the tests, and indicatesthe advantage to be deri
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