. The Bell System technical journal . ^,^ _ VOICE BANDS CHANNEL DEMODULATOR INPUT 108 D -104 l±. I5 D I 8- GROUP DEMODULATORINPUT 12 . I i°— ^-D*32 I---438 I ^-4,6 I1-°.I2J 1/ D 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 modu
. The Bell System technical journal . ^,^ _ VOICE BANDS CHANNEL DEMODULATOR INPUT 108 D -104 l±. I5 D I 8- GROUP DEMODULATORINPUT 12 . I i°— ^-D*32 I---438 I ^-4,6 I1-°.I2J 1/ D 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 VOICE TERMINATING CHANNEL MODEMS CIRCUITS I , MODULATORS, DE- MODULATORS ANDDEMODULATOR|yQI(-g 1, AMPLIFIERS ^ CIRCUITS Tp UU ♦r UU 1 64 - MODULATOR ANDDEMODULATORBAND FILTERS. Fig, 2—Block schematic. 110 BELL SYSTEM TECHNICAL JOURNAL >■ Q .ujo3 mjm u lllllllllllllllll J Ki m <N u iiiiiiiiiiiiimimi u ff ofc$!:i
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
