1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 - TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU-!).4%.!.#% ).4%2.!4)/.!,G0G0,%!3%$G0G0#)2#5)43#/.34)454)/.G0G0!.$G0G0./-%.#,!452%/b) the circuit may be available either 2-wire or 4-wire at a renters installation1);c) the transmission paths may be provided
2、 with a combination of unloaded (or loaded) subscribers line plant(in the local network), unloaded or loaded cable pairs (in the junction network) channels in frequencydivision multiplex carrier systems (in the national long-distance network and in the internationalnetwork), and channels in time div
3、ision multiplex transmission systems (in the national or internationalnetwork).Figure 1/M.1010 illustrates two types of circuits: those which connect two points and those connecting morethan two points. These are referred to as point-to-point circuits and multiterminal circuits respectively.d01-scFI
4、GURE 1/M.1010.D01_1)Some Administrations do not provide the 2-wire facility for special quality international based circuits.2 Fascicle IV.2 - Rec. M.10102 Access points2.1 It is recommended that Administrations establish access points on the various circuit sections analogous to theaccess points re
5、commended for international telephony circuits in the public service at which the nominal relative levelsare fixed and determined by the Administration. At the international centre it would be advantageous if the same relativelevel as that adopted for public circuits is used for leased circuits. Wit
6、hin the national networks there are very oftenaccess points of defined relative level and impedance provided in accordance with national practices and these points,together with the international access points, serve to divide the circuit into circuit sections.2.2 In principle, an access point is al
7、so available at the renters premises but it is not always convenient to testfrom there. Accordingly, the procedures recommended in this Section involve also the access points provided byAdministrations in repeater stations or telephone exchanges near to the renters installation for transmissionmeasu
8、rements on international leased circuits.These are points between which it might be expected that measurements could be made, though the staff atsuch stations concerned do not always have experience in international maintenance procedures. Measurements made byAdministrations between renters installa
9、tions could encounter particular problems.3 Definitions and nomenclatureThe definitions below are illustrated in Figure 2/M.1010.d02-scFIGURE 2/M.1010.D023.1 international leased circuitThe whole of the assembly of lines and apparatus connecting the renters terminal equipment (e.g. datamodem) in one
10、 country to the renters terminal equipment in another. The interfaces between the circuit and the rentersterminal equipment will be defined by the respective Administrations.3.2 international linkThe whole of the assembly of international and national circuit sections between terminal national centr
11、es.3.3 international lineThe whole of the assembly of international and national circuit sections between terminal international centres.Fascicle IV.2 - Rec. M.1010 33.4 national lineThe whole of the assembly of national circuit sections connecting the terminal national centre to the terminalinterna
12、tional centre. When a distinction is needed to indicate the transmission direction in one country the expressionsnational sending line, that is, outgoing from the renter, and national receiving line, that is, incoming to the renter, maybe used.3.5 terminal international centreThe terminal internatio
13、nal centre (TIC) for leased and special circuits is the international centre serving therenter in the country in which the renters installation is situated. It marks the interface of the international and nationallines and is normally located in association with a terminal international centre for i
14、nternational public telephonycircuits.Some Administrations may wish to locate the TIC for international leased and special circuits independently ofthat for public telephony circuits.In all cases there will be a transmission maintenance point (international line) (TMP-IL) (see RecommendationM.1014)
15、located at each TIC for leased and special circuits.There will be two TICs in a point-to-point international circuit. There may be more in a multiterminal circuit.3.6 terminal national centreThe national centre (e.g. repeater station, telephone exchange) that is: nearest to the renters installation,
16、 provided with a circuit test point, so that transmission measurements can be made by appropriate staff.3.7 terminal national sectionThe lines and apparatus connecting the renters installation with the terminal national centre concerned. Theremay be intermediate installations (e.g. telephone exchanges) in the terminal national section but they are assumed tohave no testing facilities normally available.
