The CCITT,considering(a) that it is necessary to define the overall maximum transfer delay and its distribution between national and international circuits;(b) the need to divide the responsibility between Administrations involved in establishing international switching connections;(c) that there are difficulties in specifying standard limits on transfer delay in a single telegraph channel on account of the variation in length and numbers of telephone channels connected in tandem on the bearer circuit;(d) that the use of satellite communication links in the international telegraph, telex and gentex networks and the Maritime Mobile Service is increasing;(e) that the increase in the signal transfer delay caused by the conditions mentioned above requires the specification of tolerable limits on signal transfer delay in the hypothetical reference connection;(f) that the transfer delays on signalling elements inherent in the signalling types specified in the Series URecommendations will be considerable on multiple tandem sections;(g) the provision for hypothetical reference connections contained in Recommendation U.8.
ITU-T R.58 BIS-1988 Referenced Document
ITU-T U.8 Hypothetical Reference Connections for Telex and Gentex Networks - Telegraph Switching (Study Group IX) 5 pp*， 1989-01-01 Update
ITU-T R.58 BIS-1988 history
1988ITU-T R.58 BIS-1988 LIMITS ON SIGNAL TRANSFER DELAY FOR TELEGRAPH, TELEX AND GENTEX NETWORKS