. The Bell System technical journal. Telecommunication; Electric engineering; Communication; Electronics; Science; Technology. 196 BELL SYSTEM TECHNICAL JOURNAL to so-called transient effects. That is, the currents, after arriving at the distant end of the communication circuit, require an appreciable time, varying with the impressed frequency, to build up and, under certain conditions, may never build up to anything remotely resembling the transmitted currents in the short interval during which the latter exist. This effect, moreover, may produce serious impairment in the quality of the recei
. The Bell System technical journal. Telecommunication; Electric engineering; Communication; Electronics; Science; Technology. 196 BELL SYSTEM TECHNICAL JOURNAL to so-called transient effects. That is, the currents, after arriving at the distant end of the communication circuit, require an appreciable time, varying with the impressed frequency, to build up and, under certain conditions, may never build up to anything remotely resembling the transmitted currents in the short interval during which the latter exist. This effect, moreover, may produce serious impairment in the quality of the received speech or signal even when the line is so designed that the steady state attenuation of all currents in the essential range is substantially 0 03 TIME IN SECONDS Fig. 1—Building-up of current on 1500 mile telegraph cable As an illustration of the transient distortion on a transmission line, consider the indicial admittance, A{t), of the cable of length / miles, and of resistance R and capacity C per mile; that is, the received current in response to a unit voltage applied at the sending end at time / = 0. This is given by ^ A{t) = 2_ e^ Rl -yjy ' where 4/ RCP Curve (1) of Fig. 1 represents relative values of A{t) on a cable 1,500 miles long. (This is the same cable whose phase characteristic is shown in Fig. 5, the inductance being ignorable in determining the indicial admittance.) The departure of the received current from the abrupt wave front of the impressed voltage is clear. ^ See reference Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original American Telephone and Telegraph Company. [Short Hills, N. J. , etc. , American Telephone and Telegraph Co. ]
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