. The Bell System technical journal . designed to transmit frequencies between approximately200 and 2,600 cycles. Of course, the higher the cut-off frequency, themore expensive will be the loading. Practical reasons make it desir-able to space the loading coils on the cable circuits connecting withnon-loaded open wire lines at the same intervals as the coils whichare used on the cable circuits connected with the loaded open wirelines. This consideration in combination with the nominal impedance IOR cih(rrrs 261 rcquirenieiit prcxiousK meiitioiud, fixes the cut-olT charac
. The Bell System technical journal . designed to transmit frequencies between approximately200 and 2,600 cycles. Of course, the higher the cut-off frequency, themore expensive will be the loading. Practical reasons make it desir-able to space the loading coils on the cable circuits connecting withnon-loaded open wire lines at the same intervals as the coils whichare used on the cable circuits connected with the loaded open wirelines. This consideration in combination with the nominal impedance IOR cih(rrrs 261 rcquirenieiit prcxiousK meiitioiud, fixes the cut-olT characteristics and,hence, the slope of the termination inii:)e(hince-freqnency general considerations ha\e led to the standar(lizatif)n of the£-28-10 loadint;- s\-steni for nse on entrance cable and inierniediatccable condnctors associated with non-loaded open wire lines, (ieneraldata for this system are given in Table XII, and the computed im-pedance characteristics are illustrated in JMg. 14, also gixes 1000. -400 L^0 800 1600 2400 3200FREQUENCY-CYCLES 4000 Fig. 14—-Typical impedance-frequency characteristics of loaded and non-loadedentrance cable and non-loaded open wire line the characteristic impedance curves for the non-loaded open wire lineand the non-loaded cable. Since the E-28-16 loading system is a lowimpedance loading, the attenuation improvement is small relativeto that of other types of loading system which are primarily installedfor attenuation improvement. Table XII also gives general data regarding the M-44-2r) entrancecable loading system which has been used to some extent as a sub-stitute for the E-28-1G loading system on cables connected to non-loaded open wire lines. The M-44-25 system used higher inductance 262 BELL SYSTEM TECHNICAL JOURNAL loading coils and consideraiily longer spacing intervals than the{£-28-16 system, and was consequently less expensive. The impe-dance characteristics, however, were not so satisfactory at the
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