1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 % TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%0(/.%G0G0.%47/2+G0G0!.$G0G0)3$./0%2!4)/. G0G0.5-“%2). G0G02/54).!.$G0G0-/“),%G0G03%26)#%$%6)#%3G0G0 for themeasurements in question, the current strength in the meter is at all times proportional to the n
2、umber of circuits or unitsof 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 accuracyof the latter is not so good for intensities which a
3、re only a small fraction of the nominal intensity for whichthe 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 observ
4、ed;d) voltage variations in the supply battery used.Obviously, the longer the period of observation, the greater are the chances that partial compensations willoccur between the various causes of error. With such apparatus it seems unlikely that more than a 2% accuracy ofmeasurements can be obtained
5、 for measurements made over an adequate period of time which includes hours ofvarying load; measurements made only at times when there is very little traffic might involve a considerably greatererror.2 Use of pulse-counting metersWith this method, the circuits or equipment under observation are conn
6、ected, for the duration of a call, to pulse-counting meters which receive pulses from a common timing mechanism at suitable intervals, for example every sixseconds. The call duration is deduced from the meter readings.3 Use of a device for periodically scanning circuits or equipmentThese devices can
7、 be based on either the conventional type of equipment (relays, crossbar switch, etc.) or someform of electronic equipment.4 Degree of accuracy of methods 2 and 3With the two last-named methods, the degree of accuracy of measurements depends on: the average call duration and the statistical distribu
8、tion 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
9、 the meter in method 3, or from accidental variations in the pulsing orscanning interval.There is no doubt that if the number of calls observed is sufficiently high it is possible, using these methods andwithout reducing the pulse-sending interval or the scanning interval to such a small value that
10、operation difficultieswould arise with classic-type apparatus, to obtain greater accuracy than could be obtained with the method described in 1 above.2 Fascicle II.2 - Rec. E.2615 Fault indicationIt is recommended that provision should be made for indicating faults in the measuring and recording dev
11、ice.There are two possibilities:a) to design the measuring and recording apparatus so that there is a permanent check on its operation, withan alarm system to indicate faults;b) to provide special equipment to make a routine check of the operation of the measuring equipment.6 Equipment designThe des
12、ign of equipment for measuring and recording call durations is left to Administrations. Someinformation will be found in Annex A.ANNEX A(to Recommendation E.261)Measuring call durationA.1 The technique to be adopted for recording call durations of automatic traffic will depend on the accountingarran
13、gements agreed between Administrations and particularly on whether recordings are to be made: by country of destination alone; by route and country of destination; by route, country of destination and charging zone.In all cases it will be necessary to discriminate between automatic and semiautomatic
14、 traffic and possibly transittraffic.A.2 Assuming that it is possible to identify automatic calls on the outgoing international circuit and that the circuitscarry only terminal traffic, the measurement of call durations could be effected by connecting a measuring andrecording device to each internat
15、ional circuit. The disadvantage of this scheme is the large number of recorders to beprovided and read daily.A single recorder could be made to serve a group of international circuits by arranging for the recorder to beconnected to each circuit of a group in turn, say every six seconds, and for the
16、recorder to operate each time that aninternational circuit in the answered condition is encountered. The recorder would then show then show the total callduration of the circuit group.A.3 Where transit routings are involved and the recordings are required on the basis of route and country ofdestinat
17、ion, separate totals of call durations will be required for each country served by the route in question. In otherwords, it will be necessary to determine the destination of each call and record the call duration on the appropriaterecorder.This may be found to be a complicated process and it may be
18、more convenient to connect the recorder at a pointremote from the international circuit, for example at the register access relay set, where information in respect of thedestination and routing of the call can be obtained from the outgoing international register. Figure A-1/E.261 illustratesan arran
19、gement in which the selector A is positioned under the control of the register to connect the appropriate routeand destination recorder to the register access relay set.The recorder could be an ampere-hour meter or it could consist of a meter and a selector arranged to scan allthe register access re
20、lay sets which have been connected to this particular route and destination recorder.Fascicle II.2 - Rec. E.261 3A.4 A similar arrangement to Figure A-1/E.261 can be employed where recordings are required on the basis ofroute, country of destination and charging zone. The additional complications in
21、troduced in determining the chargingzone mainly concern the outgoing register but it should be noted that a greater number of separate call durationrecorders will then be needed.A.5 The number of recorders or separate records of call durations is equal to the summation, for all destinations, ofthe p
22、roduct of number of routes by number of charging zones for each country of destination. The capacity of selectorA in Figure A-1/E.261 must be sufficient to permit access to any recorder and the economics of this scheme will bedetermined by the number of separate recordings required and the total vol
23、ume of international traffic originated at theexchange concerned.A.6 For a large number of separate recordings, Administrations might consider whether it would be cheaper to useelectronic methods for recording call durations. In this connection Administrations might take into account the possiblefuture introduction of cheap rates which could double the number of separate records required.
