. The Bell System technical journal . simulators; hence the process of temperature compensation con-sists, effectively^ in adding cable when the temperature falls and re-moving it when the temperature rises. 23-i THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1957 At Terrenceville, the networks permit adjustments equivalent to±1 nautical mile of cable (3 db at 552 kc), but at Clarenville and Syd-ney Mines adjustments equivalent to db at 552 kc are provided. Itshould therefore always be possible to maintain the overall loss of thesystem within ± db, and the level at any repeater should neve
. The Bell System technical journal . simulators; hence the process of temperature compensation con-sists, effectively^ in adding cable when the temperature falls and re-moving it when the temperature rises. 23-i THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1957 At Terrenceville, the networks permit adjustments equivalent to±1 nautical mile of cable (3 db at 552 kc), but at Clarenville and Syd-ney Mines adjustments equivalent to db at 552 kc are provided. Itshould therefore always be possible to maintain the overall loss of thesystem within ± db, and the level at any repeater should neverchange by more than ±2 db. System Pilots The use of pilot tones applied at constant level at the input of asystem with indicating or alarm meters at the receiving end is standardon land systems on both sides of the Atlantic, although the philosophiesunderlying the methods of use differ. On the submarine cables round theBritish Isles, with or without submerged repeaters, pilot tones are used SYDNEY MINES TERRENCEVILLE CLARENVILLE. AT MINIMUM TEMPERATURE Fig. 10 — Deviation from mean of transmission levels with optimum adjust-ments of equalizers at Sjdney Mines, Terrenceville and Clarenville. ^ W-E at 260 kc. ■ E-W at 552 kc. jVIaximum deviation in the two directions occurs at the above frequencies. SYSTEM DESIGN ^ NEWFOUNDLAND-XOVA SCOTIA LINK 235 to indicate the attenuation of the transmission path; these pilots arenormally located just outside the main transmission bands in eachdirection. In the Clarenville-Sydney Mines system the frequency bandsjust outside the main transmission bands are occupied by telephonespeaker and teleprinter circuits and by monitoring frequencies associatedwith the repeaters (see Fig. 5); this prevents the use of out-of-band pilots. Fortunately, the standard Bell System group equipment is designedto apply 92-kc pilots to each group and to measure the correspondingreceived level. Although these are essentially group pilots, being appliedand mea
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