. The Bell System technical journal . CARRIER IN CABLE 261 VARIABLE RESISTANCES FOR CONTROL OF <12 INDIVIDUAL LINES MOTOR GEARED TO SHAFT-*-*. .MASTER CONTROL/ MECHANISM Fig. 8—Automatic transmission regulating equipment—covers removed. 262 BELL SYSTEM TECHNICAL JOURNAL Obtaining High Amplifications The attenuation of cable pairs being inherently high at carrierfrequencies, high amplifier gains are called for, otherwise the cost ofthe carrier circuits goes up very materially. Since as the powercarrying capacity of the repeaters is increased a point is soon reachedwhere it becomes very expen
. The Bell System technical journal . CARRIER IN CABLE 261 VARIABLE RESISTANCES FOR CONTROL OF <12 INDIVIDUAL LINES MOTOR GEARED TO SHAFT-*-*. .MASTER CONTROL/ MECHANISM Fig. 8—Automatic transmission regulating equipment—covers removed. 262 BELL SYSTEM TECHNICAL JOURNAL Obtaining High Amplifications The attenuation of cable pairs being inherently high at carrierfrequencies, high amplifier gains are called for, otherwise the cost ofthe carrier circuits goes up very materially. Since as the powercarrying capacity of the repeaters is increased a point is soon reachedwhere it becomes very expensive to go further, high amplificationsmust be secured by letting the transmitted currents become veryweak before amplifying them. A natural limit to this is found in theso-called thermal or resistance noise ^ generated by all natural and largely insuperable noises are introduced by thevacuum tubes in the amplifiers. Other sources of noise are: 1. Telegraph and signaling circuits worked on other pairs in the same cable with the carrier circuits. 2. Radio stations. 3. Noise from power systems, particularly electric ra
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
