1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 - TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU-!).4%.!.#%G0 ).4%2.!4)/.!,G0G04%,%0(/.%G0G0#)2#5)430%2)/$)#)49G0G0/b) overall loss and levels at several frequencies;c) stability (for two-wire audio circuits or sections of circuit only);d) signalling;e) no
2、ise;f) echo control devices.The periodicity for measurements of loss, noise, stability and signalling is given in Tables 1/M.610and 2/M.610; in addition, other types of measurements are given in Table 1/M.610 for which the periodicity may bedetermined by the Administrations concerned.Table 1/M.610 s
3、hows the periodicity for measurements on the types of circuit normally used in theinternational telephone network (except for frontier circuits). When automatic transmission measuring and testingequipments are available, transmission measurements and signalling tests may be carried out more frequent
4、ly thanindicated in this table.Echo control devices (echo suppressors or cancellers) may be tested using semi-automatic/automatic testinstruments or facilities when such are deployed by Administrations. If semi-automatic/automatic instruments, etc., arenot available, Administrations should agree bil
5、aterally regarding these tests.These circuits are: 4-wire audio-frequency circuits. Included also in this category are circuits on carrier systems providing asmall number of telephone channels. No distinction is made between circuits in underground cables andcircuits on open-wire lines unless the op
6、en-wire section is equipped with repeaters; 4-wire carrier circuits on telephone channels of systems providing at least one group; 4-wire circuits of mixed constitution, i.e. consisting of a mixture of audio and carrier sections.Table 2/M.610 shows the periodicity of measurements to be made on short
7、-distance international circuits thatare generally used for terminal traffic, but which can, when necessary, be used to extend more important internationalcircuits. It is desirable that the same recommendations be applied to national circuits that are frequently used forinternational communications.
8、_1)This is the general rule. In a few exceptional cases, however, routine measurements may be found desirable on constituentelements of circuits if they can give indications not otherwise readily obtained. For example, in accordance withRecommendation G.131 2.4 1, echo suppressors are not necessaril
9、y permanently associated with circuits and must then bechecked by separate in-station tests as provided in Recommendation M.660. Also, in some special cases mentioned in theintroductory notes to that Recommendation, the complete-circuit measurements afforded by the ESTS instrument, specified inRecom
10、mendation O.25 2, might be found inadequate.2 Fascicle IV.1 - Rec. M.610TABLE 1/M.610Periodicity of measurements and tests to be made on international telephone circuits(circuits normally used in the international network)Column 1 Column 2 Column 3 Column 4 Column 5 Column 6 Column 7Systematicsubjec
11、tive testingSignalling tests Echo control devicesTypeof DescriptionMeasurement ofoverall loss atone frequencyMeasurements ofoverall loss atSignal-to-crosstalkratio betweenCircuit and measurementof noise a)severalfrequenciesgo and return pathsManual Automatic Suppressorsb)Cancellersc)Frequencytransla
12、tion errorcircuits circuitsAudio1 to 14 repeaters Monthly Half-yearlyTo be tested at Testing to followfrequency4-wire15 or more repeaters Weekly Half-yearlythe same time asthe measurementthe Series QRecommenda-Same, with open-wiresection with at leastone repeaterAt least monthlyor as agreedHalf-year
13、lyNone of overall loss atseveralfrequenciestions6 months 6 monthsWhollycarrierCircuits set up onchannels on a simplegroup link andterminating at the samepoints as the groupTwo-monthly oras agreedYearly As agreed inaccordance with needand experienceCircuits routed overseveral groupsMonthly Yearly As
14、agreed inaccordance with needand experience4-wirecircuitsof mixedconstitutionAt least monthlyor as agreedYearly As agreed inaccordance with needand experiencea)Measurements of overall loss at one frequency and of noise shown in column 3 are included in the measurements made at several frequencies sh
15、own in column 4.b)Assumes the use of an echo suppressor test facility as part of an ATME as specified in Recommendation O.22 3.c)Assumes the use of an echo canceller test facility as part of an ATME as specified in Recommendation O.22 3.Fascicle IV.1 - Rec. M.610 3TABLE 2/M.610Periodicity of measure
16、ments to be made on international telephone circuits(Types of circuit not normally used in the international network)References1 CCITT Recommendation Stability and echo, Vol. III, Rec. G.131.2 CCITT Recommendation Semi-automatic in-circuit echo suppressor testing system (ESTS), Vol. IV Rec. O.25.3 C
17、CITT Recommendation CCITT automatic transmission measuring and signalling testing equipment ATMENo. 2, Vol. IV, O.22.Column 1 Column 2 Column 3 Column 4 Column 5 Column 6Category Type of circuitMeasurementsof overall lossat oneMeasurementsof overall lossMeasurementsSignalling testsof circuit frequen
18、cy andmeasurementof noisea)at severalfrequenciesof stabilityManualcircuitsAutomaticcircuits2-wire circuits with onerepeaterYearly Yearly Yearly2-wire circuits withtwo or three repeatersHalf-yearly Yearly Half-yearlyAudio-frequency2-wire circuits with atleast four repeatersQuarterlyMonthlyHalf-yearly
19、Half-yearlyQuarterlyMonthlyAt the sametime asmeasurementsof overall lossand levels atAs agreedbetweenAdministrations2-wire circuitsincluding an open-wire section with atleast one repeaterseveralfrequencies(see column 4)4-wire circuits with a2-wire section havingat least one repeaterAs agreed between Administrationsa)Measurements of overall loss at one frequency and of noise shown in column 3 are included in the measurements made atseveral frequencies shown in column 4.
