. The Bell System technical journal . T (b) close and close CIRCUIT. T T (c) open and open circuit Fig. 5—Explanation of electronic loop circuit. 676 THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1952 During open-and-close transmission by the subscriber, the high im-pedance termination of the loop at the tetrode plate circuits causes thecurrent at the central office end of the loop to change very slowly—tooslowly for good transmission at teletypewriter speeds. However, thevoltage wave is very well shaped, and this is what is used to drive thegrid of the transmitting tube. One noteworthy fact is that
. The Bell System technical journal . T (b) close and close CIRCUIT. T T (c) open and open circuit Fig. 5—Explanation of electronic loop circuit. 676 THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1952 During open-and-close transmission by the subscriber, the high im-pedance termination of the loop at the tetrode plate circuits causes thecurrent at the central office end of the loop to change very slowly—tooslowly for good transmission at teletypewriter speeds. However, thevoltage wave is very well shaped, and this is what is used to drive thegrid of the transmitting tube. One noteworthy fact is that the bias ofthe signals repeated from loop to line is nearly independent of loop length;consequently no inductive wave shaping is required at the subscriberstation, even in the longest operable loops. Because of the high impedance termination, loop current is insensitiveto circuit resistance. The loop padding rheostat is, therefore, adjustedto build out the loop resistance to a standard value and the amount ofloop current required for proper operation of the s
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
