. The Bell System technical journal . *32 -^32 1 1 \ 30 - i-S*26 -^ 30 - ^-Jl2S 1 1 \ U-ILa4 ■ ^-4^4 1 \1 \ |3 D 3 □ ,„ 20 / -—y»20/ 1 U-il,6 20 -—f^20 1 1 \ \ / j a__D„2 ^-9 \ 10 10 1 \ 1 \ 0 Illlllllllll 0 llllilllllll VOICE BANDS VOICE BANDS Fig. 1—Frequency allocation. From the terminating equipment the circuit loops through jackswhich have paralleled contacts for reliability. The level at this pointis - 13 db compared with the transmitting toll switchboard, whichlevel is expected to be generally used in the Bell System for all multi-channel carrier telephone systems. Then comes th
. The Bell System technical journal . *32 -^32 1 1 \ 30 - i-S*26 -^ 30 - ^-Jl2S 1 1 \ U-ILa4 ■ ^-4^4 1 \1 \ |3 D 3 □ ,„ 20 / -—y»20/ 1 U-il,6 20 -—f^20 1 1 \ \ / j a__D„2 ^-9 \ 10 10 1 \ 1 \ 0 Illlllllllll 0 llllilllllll VOICE BANDS VOICE BANDS Fig. 1—Frequency allocation. From the terminating equipment the circuit loops through jackswhich have paralleled contacts for reliability. The level at this pointis - 13 db compared with the transmitting toll switchboard, whichlevel is expected to be generally used in the Bell System for all multi-channel carrier telephone systems. Then comes the channel modula-tor which consists of four copper-oxide discs, each three-sixteenths of aninch in diameter, potted in a small can. This makes a very simple andinexpensive modulator which is much more satisfactory than tubes. CABLE CARRIER TELEPHONE TERMINALS 109 I VOICE TERMINATING CIRCUITS I MODULATORS, DE-MODULATORS ANDDEMODULATORI yQ|(.g ^ AMPLIFIERS ^ CIRCUITS Fa CHANNEL MODEMS MODULATOR ANDDEMODULATORBAND FILTERS. Fig. 2—Block schematic. no BELL SYSTEM TECHNICAL JOURNAL I >- Q7:< iiil^8K^ T\m I—nsfs^—I
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
