ITU-T E.261-1988 测量和记录呼叫时间的装置 Devices for measuring and recording call durations

pdf标准 ITU-T E.261-1988 测量和记录呼叫时间的装置 Devices for measuring and recording call durations

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ITU-T E.261-1988 测量和记录呼叫时间的装置 Devices for measuring and recording call durations 第 1 页 ITU-T E.261-1988 测量和记录呼叫时间的装置 Devices for measuring and recording call durations 第 2 页 ITU-T E.261-1988 测量和记录呼叫时间的装置 Devices for measuring and recording call durations 第 3 页 ITU-T E.261-1988 测量和记录呼叫时间的装置 Devices for measuring and recording call durations 第 4 页 ITU-T E.261-1988 测量和记录呼叫时间的装置 Devices for measuring and recording call durations 第 5 页
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国外分类,ITU,ITU-T(电信标准分局),itu,测量,记录,呼叫,时间,装置,devices,for,measuring,and,recording,call,durations

INTERNATIONAL TELECOMMUNICATION UNION )45 4 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU 4%,%0(/.% .%47/2+ !.$ )3$. /0%2!4)/. .5-"%2).' 2/54).' !.$ -/"),% 3%26)#% $%6)#%3 &/2 -%!352).' !.$ 2%#/2$).' #!,, $52!4)/.3 )45 4 Recommendation % (Extract from the "LUE "OOK) % NOTES 1 ITU-T Recommendation E.261 was published in Fascicle II.2 of the Blue Book. This file is an extract from the Blue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, the contents of the file are identical to the Blue Book version and copyright conditions remain unchanged (see below). 2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. © ITU 1988, 1993 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. Recommendation E.261 Fascicle II.2 - Rec. E.261 DEVICES FOR MEASURING AND RECORDING CALL DURATIONS There are three main methods used for measuring call duration: 1 Use of apparatus of the type which meters the quantity of electricity (ampere-hour meter or coulombmeter) This type of meter is permanently connected to the circuits or equipment under observation; for the measurements in question, the current strength in the meter is at all times proportional to the number of circuits or units of equipment in the speech position. With this type of apparatus the accuracy of the measurements depends on: a) errors in the meter (shunt included) itself; in any case, in the absence of special arrangements, the accuracy of the latter is not so good for intensities which are only a small fraction of the nominal intensity for which the apparatus is designed; b) the accuracy and possibly the variations with time of the resistors inserted in the circuits to be observed; c) the ohmic resistance of the connections between the measuring equipment and the circuits to be observed; d) voltage variations in the supply battery used. Obviously, the longer the period of observation, the greater are the chances that partial compensations will occur between the various causes of error. With such apparatus it seems unlikely that more than a 2% accuracy of measurements can be obtained for measurements made over an adequate period of time which includes hours of varying load; measurements made only at times when there is very little traffic might involve a considerably greater error. 2 Use of pulse-counting meters With this method, the circuits or equipment under observation are connected, for the duration of a call, to pulsecounting meters which receive pulses from a common timing mechanism at suitable intervals, for example every six seconds. The call duration is deduced from the meter readings. 3 Use of a device for periodically scanning circuits or equipment These devices can be based on either the conventional type of equipment (relays, crossbar switch, etc.) or some form of electronic equipment. 4 Degree of accuracy of methods 2 and 3 With the two last-named methods, the degree of accuracy of measurements depends on: − the average call duration and the statistical distribution of call durations; − the number of calls observed; − the interval between the sending of pulses (method 2) or the scanning interval (method 3). It is also possible to assess mathematically, as a function of these factors, the anticipated degree of accuracy. Errors may also arise from the operation of the meter in method 3, or from accidental variations in the pulsing or scanning interval. There is no doubt that if the number of calls observed is sufficiently high it is possible, using these methods and without reducing the pulse-sending interval or the scanning interval to such a small value that operation difficulties would arise with classic-type apparatus, to obtain greater accuracy than could be obtained with the method described in § 1 above. Fascicle II.2 - Rec. E.261 1 5 Fault indication It is recommended that provision should be made for indicating faults in the measuring and recording device. There are two possibilities: a) to design the measuring and recording apparatus so that there is a permanent check on its operation, with an alarm system to indicate faults; b) to provide special equipment to make a routine check of the operation of the measuring equipment. 6 Equipment design The design of equipment for measuring and recording call durations is left to Administrations. Some information will be found in Annex A. ANNEX A (to Recommendation E.261) Measuring call duration A.1 The technique to be adopted

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