1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 . TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU-!).4%.!.#%G0G0/ and preparatory periodThe period during which the broadcasting organizations carry out their own adjustments, tests, etc., beforethe television transmission itself commences.The exact time at
2、 which the preparatory period begins (point H on Figure 1/N.54) is determined by thebroadcasting organizations.2 Line-up periodIt is provisionally recommended that, in principle, the duration of the line-up period should nominally be30 minutes, subdivided into two periods, for the operations describ
3、ed below (see Figure 1/N.54).d01-scFIGURE 1/N.54.D01H 30 to H 15: Concurrent lining-up of the national and international circuit sections that will be used toconstitute the international television circuit. The international circuit sections may or may not include a communicationssatellite. The test
4、s to be made are those given in Recommendation N.62. Tests between the earth stations of acommunications satellite circuit section are not the responsibility of the CCITT but these tests also should be completedby time H 15.2 Fascicle IV.3 - Rec. N.54H 15 to H: Interconnection of the circuit section
5、s to be used, confirmation that the international televisioncircuit is continuous between the terminal ITCs and overall tests between the control ITC and the sub-control ITC. Thetests to be made are those given in Recommendation N.621).The above periods H 30 to H 15 and H 15 to H are indicated for g
6、uidance only. Their duration is based onan estimate of the time necessary to perform the tests in Recommendation N.62 with a reasonable allowance foradjustments. No allowance is included for the removal of fault conditions on the circuit sections or on the completecircuit link.These periods also ass
7、ume a configuration of the international television circuit2)consisting of oneinternational circuit section extended at each end by one national circuit section. In the case of television transmissionsinvolving more than two countries, either or both of the nominal periods H 30 to H 15 and H 15 to H
8、 may have to beincreased. On the other hand, in particular cases, either or both of these nominal periods may be reduced, by agreementbetween the Administrations concerned, provided the line-up is properly carried out. This may be possible, for example,when there are two successive international tel
9、evision transmissions on the same route, and the second involvesextending the international television circuit or link already lined-up for the first.During the last few minutes of the nominal period H 15 to H, when the above tests have been completed, thecontrol and sub-control ITCs3)should put the
10、 link through to the broadcasting organization at each end and shouldconfirm that the complete connection is continuous. It should be verified that the link2)is satisfactory for transmitting theprogramme, and that the quality and level are acceptable.By agreement between the telecommunication Admini
11、stration and the sending broadcasting organization, itmight be desirable, during these last few minutes before the end of the line-up period, to transmit live pictures. Thiswould be of particular use when adjusting standards converters. The transmission of live pictures during the line-upperiod does
12、 not, however, alter the telecommunication Administrations responsibility with regard to the quality oftransmission required. This responsibility begins only at time H, when the line-up period ends and the preparatory(service) period begins, and when the link is handed over to the broadcasting organ
13、izations.3 Preparatory periodNo definite duration is recommended by the CCITT for the preparatory period. This duration is determined bythe broadcasting organizations, but a typical duration is 15 minutes. During this period, the tests to be made are also leftto the discretion of the broadcasting or
14、ganizations, but they must not be such as to depart from CCITT recommendationsin respect of signal level (see Recommendations N.60 and N.63). The broadcasting organizations may, on occasion, omitthe preparatory period and begin the actual transmission at time H._1)See the comment in Recommendation N
15、.62 concerning the difficulties involved in making overall tests on circuits that include astandards converter.2)According to the definitions given in Recommendation N.51 in this particular case, the international television circuit is also aninternational television link.3)See Recommendation N.55 for definition of control and sub-control ITCs.
