1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 3 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%2!0(9!,0(!“%4)#!,G0G04%,%2!0(G0G04%2-).!,%15)0-%.4!.37%2G0G13G0“!#+G0G05.)43amended at Geneva, 1976)The CCITT,considering(a) that start-stop machines are capable of receiving communications without the ai
2、d of an operator;(b) that it may be necessary to verify the correct functionning of the line and of the distant terminal equipment,unanimously declares the viewthat if the use of an automatic answer-back unit is requested, it would be advisable:1) to effect the operation of code transmitter by the c
3、ontrol character ENQ, position 0/5 in the code table ofInternational Alphabet No.5 (Recommendation T.50 1);2) to compose the code-emission by a series of 20 signals, as follows:1 CR (position 0/13 in the code table),1 LF (position 0/10 in the code table),2 non-printing, non carriage moving signals (
4、but which may include CR),16 signals chosen for the subscriber comprising the identification of the machine;3) when the code signal does not comprise 16 characters, to distribute them by inserting at the beginning asmany fill signals (sush as DEL or NUL) as are necessary to make up the total of 16 s
5、ignals;4) that the answer-back signals follow Recommendations X.4 2 and S.31;5) that the delay between the reception of the beginning of the start unit of control character ENQ and thebeginning of the start unit of the first signal of the answer-back sent by the machine should lie between oneand four character periods.References1 CCITT Recommendation International Alphabet No.5, Rec. T.50.2 CCITT Recommendation General structure of signals of International Alphabet No. 5 code for datatransmission over public data networks, Rec. X.4.
