1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU).4%2.!4)/.!,G0G0!.!,/5%G0G0#!22)%2G0G03934%-3%.%2!,G0G0#(!2!#4%2)34)#3G0G0#/-/.G0G04/G0G0!,!.!,/5%G0G0#!22)%2G0G13G042!.3-)33)/.G03934%-34(2/5(G0G13G0#/%#4)/.G0G0/ further amended)1 General considerations1)It
2、may be found desirable from both the technical and the economical points of view to provide facilities at theend of certain sections such that the channels routed over one section do not all have to be extended to the next section,this being done without demodulating all the channels to voice freque
3、ncy, whole batches of channels being extended todifferent line sections.At such points, which are at the ends of the line links concerned, the through-connection of batches of telephonechannels should be possible from one line link to another. This can be achieved by means of the following two metho
4、dswhich, though basically different, can nevertheless be used in association at a given point for different batches ofchannels. In both cases arrangements are necessary to ensure that the through-connected frequency band is “clear“, thatis to say, as far as possible the channel vestiges on the two s
5、ides of the through-connected batch of channels should besuppressed by means of a through-connection filter.1.1 Through-group, supergroup, mastergroup, supermastergroup or 15-supergroup assemblyIt is assumed that the batch of through-connected channels occupies the frequency band of a group, supergr
6、oup,mastergroup, supermastergroup or 15-supergroup assembly, or that it can be split into several such bands. Each of thegroups, supergroups, mastergroups, supermastergroups or 15-supergroup assemblies is then brought into the basicfrequency band and is filtered in that band by means of a through-gr
7、oup filter, or through-supergroup, through-mastergroup, through-supermastergroup or through-15-supergroup assembly filter.Note - The frequency band occupied by the 15-supergroup assembly No. 3 (8620 to 12 336 kHz) is within thefrequency band occupied by the basic supermastergroup (8516 to 12 388 kHz
8、). Hence, when 15-supergroup assembliesare used in the conditions specified in Recommendation G.211 (procedure 2), 15-supergroup assembly No. 3 can bethrough-connected by means of through-supermastergroup filters.1.2 Direct through-connectionIt is also possible to through-connect a group, supergroup
9、, mastergroup, supermastergroup or 15-supergroupassembly or a batch of them by direct line filtration without demodulation and passage via the basic frequency band. It isthen necessary to have direct through-connection filters connected to the line equipment to effect the necessaryseparation. An exa
10、mple of this possibility is given in Recommendation G.333 for the 60 MHz system.In fixing the degree of suppression of unwanted components, it is convenient to use the following definitions:intelligible crosstalk componentsF: composantes de diaphonie intelligibleS: componentes de diafona inteligible
11、_1)This Recommendation does not consider certain precautions necessary for the protection of various pilots and additionalmeasuring frequencies. Such precautions are given in Recommendation G.243.2 Fascicle III.2 - Rec. G.242Transferred speech currents which can introduce intelligible crosstalk into
12、 certain channels at the pointconsidered.unintelligible crosstalk componentsF: composantes de diaphonie inintelligibleS: componentes de diafona ininteligibleTransferred speech currents which can introduce unintelligible crosstalk into certain channels at the pointconsidered.possible crosstalk compon
13、entsF: composantes possibles de diaphonieS: componentes posibles de diafonaTransferred speech currents which, at the point considered, do not intrude into the channels of other systems butwhich may do so elsewhere.harmful out-of-band componentsF: composantes extra-bandes nuisiblesS: componentes fuer
14、a de banda perjudicialesTransferred currents arising from speech, or pilots, or additional measuring frequencies, and of frequencies suchthat they will always lie outside the useful frequency band (corresponding to speech frequencies) of the carrier systems,but which may interfere with pilots or add
15、itional measuring frequencies.harmless out-of-band componentsF: composantes extra-bandes neutresS: componentes fuera de banda neutrasTransferred currents arising from speech or pilots which, at all translation points, have frequencies outside theuseful frequency band corresponding to audio frequenci
16、es or pilot frequencies.The term “wanted component“ is applied below in respect to speech band, to an 800-Hz signal with a power of1 milliwatt sent to a zero relative level point, and in respect of pilots or additional measuring frequencies, to the signal ofspecified frequency and level at the point
17、 where it is normally injected.2 Through-group connection2.1 Ratio between the wanted and unwanted componentsIn the case of through-connection of a group, the ratio between the wanted components and the variousunwanted components defined above should be:1) intelligible crosstalk components: 70 dB;2)
18、 unintelligible crosstalk components: 70 dB;3) possible crosstalk components: 35 dB wherever possible components appear;4) harmful out-of-band components: 40 dB;5) harmless out-of-band components: 17 dB.Fascicle III.2 - Rec. G.242 3All these separations must be provided by the transfer filter itself
19、. They relate to the nominal level, 84 kHzwhich is the reference frequency (close to the group pilots) at which the loss of the group transfer filter is set. At theother frequencies, account should be taken of the tolerance allowed for the distortion loss of this filter.At any temperature between 10
20、 C and 40 C, insertion loss for all the through-group connection equipment2)at any frequency of the passband (60.6 to 107.7 kHz3) should not depart from the loss at 84 kHz4)by more than 1 dB.The loss between 10 C and 40 C at 84 kHz should not differ by more than 1 dB from the loss at 25 C.Note 1 - I
21、t would be technically difficult for the CCITT to recommend a distribution of these overall limitsamong the equipments mentioned in footnote 2 on this page.Note 2 - The value of 70 dB shown in 1) and 2) above for the intelligible or unintelligible crosstalk componentsis the minimum standard value fo
22、r telephony. A value of 80 dB is recommended in the band which, in each groupadjacent to the through-connected group, corresponds to the band 84 to 96 kHz in the basic group and which maytherefore be used for programme transmissions by systems, whether or not equipped with compressors having thechar
23、acteristics defined in Recommendation J.31, 1.5 1.This condition should be fulfilled both when the adjacent group is direct and when it is inverted.Note 3 - As a consequence of the condition in Note 2 above, in each through-connected group, the valuerecommended will also be achieved in the band corr
24、esponding to the band 72 to 84 kHz in the basic group.Note 4 - The values recommended above for the intelligible or unintelligible crosstalk components are alsocompatible with the use of 15 kHz circuits (Recommendation J.21 2) and 7 kHz circuits (Recommendation J.23 3) forprogramme transmission. Con
25、sideration is given to the fact that the equipments used to set up these circuits(Recommendation J.31 1 and Annexes, Recommendation J.34 4) are single sideband systems with compandors ordouble sideband systems. Account was also taken of the frequency band occupied by the programme channels of theequ
26、ipments in the basic group and of the frequency response characteristics of the weighting network referred to inRecommendation J.16 5.2.2 Group-delay distortion of the through-group filterIn the case of through-connection of a group in the basic frequency band 60-108 kHz, it is recommended thatthe l
27、imits in Figure 1/G.242 for the group-delay distortion (relative to the value at 84 kHz) should not be exceeded bythe through-group filter.Note - The range of measured values on modern equipments is indicated in Supplement 17 at the end of thisfascicle._2)This equipment comprises a group demodulatio
28、n equipment, the through-group filter proper and a group modulationequipment.3)If 16-channel groups be used, the passband must be extended from 60.1 to 107.9 kHz or, by agreement between theAdministrations concerned, the band indicated in the present recommendation must be kept, in which event Note
29、1 toRecommendation G.235 will have to be carefully borne in mind.4)Slightly different loss limits apply outside the band occupied by the telephone channels when out-of-band signalling is used; thispoint can be settled on the national level or by agreement between the Administrations concerned.4 Fasc
30、icle III.2 - Rec. G.242FIGURE 1/G.2423 Through-supergroup connection3.1 Ratio between the wanted and unwanted componentsIn the case of through-connection of a supergroup, the ratio between the wanted components and the variousunwanted components defined above should be:1) intelligible crosstalk comp
31、onents: 70 dB;2) unintelligible crosstalk components: 70 dB;3) possible crosstalk components: 35 dB wherever possible components appear;4) harmful out-of-band components: 40 dB5);5) harmless out-of-band components: 17 dB._5)The specified attenuation should be met at the nominal frequencies of the pi
32、lots and additional measuring frequencies involved(at a point where these are 308 kHz or 556 kHz) in accordance with the definition of harmful out-of-band components.Fascicle III.2 - Rec. G.242 5All these separations must be provided by the through-supergroup filter itself. They relate to the nomina
33、l level412 kHz, which is the reference frequency (close to the supergroup pilots), at which the loss of the supergroup transferfilter is set. At the other frequencies, account should be taken of the tolerance allowed for the distortion loss of this filter.At any temperature between 10 C and 40 C, in
34、sertion loss for all the through-supergroup connectionequipment6)at any frequency of the passband (312.3 to 551.4 kHz should not depart from the loss at 412 kHz7)by morethan 1 dB.The loss between 10 C and 40 C at 412 kHz should not differ by more than 1 dB from the loss at 25 C.Note 1 - It would be
35、technically difficult for the CCITT to recommend a distribution of these overall limitsamong the equipments mentioned in footnote 6 above.Note 2 - The ratio of 70 dB shown in 1) and 2) above for the intelligible or unintelligible crosstalk componentsis a minimum standard value for telephony. A separ
36、ation of 80 dB is advocated for the bands liable to be used forprogramme transmission in each supergroup adjacent to the transferred supergroup.Note 3 - In the case of through-connection of supergroup 1 or 3, the range of insertion loss of the combinedthrough-supergroup equipment can reach 3 dB in t
37、he passband of the filter around 312 kHz or 552 kHz.3.2 Group-delay distortion of the through-supergroup filterIn the case of through-connection of a supergroup in the basic frequency band 312-552 kHz, it is recommendedthat the limits in Figure 2/G.242 for the group-delay distortion (relative to the
38、 value at 412 kHz) should not be exceededby the through-supergroup filter.Note - The range of measured values on modern equipments is indicated in Supplement 17 at the end of thisfascicle.FIGURE 2/G.242_6)This equipment comprises a supergroup demodulation equipment, the through-supergroup filter pro
39、per and a supergroupmodulation equipment.7)Slightly different loss limits apply outside the band occupied by the telephone channels when out-of-band signalling is used; thispoint can be settled on the national level or by agreement between the Administrations concerned.6 Fascicle III.2 - Rec. G.2424
40、 Through-mastergroup connectionFor the through-mastergroup connection, the ratio between wanted components and the various unwantedcomponents defined above should be:1) intelligible crosstalk components: 70 dB;2) unintelligible crosstalk components: 70 dB;3) possible crosstalk components: 35 dB wher
41、ever possible components appear;4) harmful out-of-band components: 40 dB8);5) harmless out-of-band components: 17 dB.All these ratios should be achieved by the through-mastergroup filter itself. They refer to the nominal level ofthe 1552-kHz reference frequency (mastergroup pilot) by which the loss
42、of the through-mastergroup filter is fixed. Atother frequencies, the attenuation/frequency distortion tolerance allowed for this filter should be taken intoconsideration.At any temperature between 10 C and 40 C, the loss at any frequency within the passband (812 to 2044 kHz)of the combined through-m
43、astergroup equipment9)should not deviate by more than 1 dB from the loss at 1552 kHz.The loss between 10 C and 40 C, at 1552 kHz, should not deviate by more than 1 dB from the loss at 25 C.Within each supergroup the total variation of the insertion loss should not exceed 1 dB relative to the loss at
44、the frequency of the supergroup reference pilot.Note - The ratio of 70 dB shown in 1) and 2) above for intelligible or unintelligible crosstalk components is aminimum standard value for telephony. A separation of 80 dB is advocated for the bands liable to be used forprogramme transmission in each ma
45、stergroup adjacent to the transferred mastergroup.5 Through-supermastergroup connectionFor the through-supermastergroup connection, the ratio between wanted components and the various unwantedcomponents defined above should be:1) intelligible crosstalk components: 70 dB;2) unintelligible crosstalk c
46、omponents: 70 dB;3) possible crosstalk components: 35 dB; wherever possible components appear;4) harmful out-of-band components: 40 dB10);5) harmless out-of-band components: 17 dB.All these ratios should be achieved by the through-supermastergroup filter itself. They refer to the nominal levelof the
47、 11 096 kHz reference frequency (supermastergroup pilot) by which the loss of the combined supermastergroupequipment11)is fixed. At other frequencies the attenuation/frequency distortion tolerance allowed for this filter should betaken into consideration._8)The specified attenuation should be met ov
48、er a band corresponding to the recommended frequency stability of the originalfrequencies of the pilots or the additional measuring frequencies involved (where these are translated to 768 kHz or 2088 kHz)in accordance with the definition of harmful out-of-band components.9)This equipment comprises a
49、 mastergroup demodulation equipment, the through-mastergroup filter proper, and a mastergrouptranslating equipment.10)The specified attenuation should be met over a band corresponding to the recommended frequency stability of the originalfrequencies of the pilots or the additional measuring frequencies involved (after frequency translation of the supermastergroupinto the basic 8516-12 388 kHz band) in accordance with the definition of harmful out-of-band com
