THE DRAWINGS CONTAINED IN THIS RECOMMENDATION HAVE BEEN DONE IN AUTOCAD.

Recommendation U.74

EXTRACTION OF TELEX SELECTION INFORMATION FROM A CALLING TELEX ANSWERBACK

(Malaga-Torremolinos, 1984; amended at Melbourne, 1988)

The CCITT,

considering

(a)	that there is a need for automatic address extraction from a telex answerback (e.g. access to a telex-Teletex conversion facility (CF) or an SFU);

(b)	that Recommendation F.60 defines a preferred structure for the telex answerback;

(c)	that different forms of answerbacks exist;

(d)	that Recommendation F.60 bis defines a structure for a telex answerback associated with an intermediate document storage device,

unanimously declares

that answerbacks are considered "technically processable" (i.e., the answerback can be interpreted unambiguously to determine the F.69 code and national call number) if they contain the minimum fields defined in Recommendation F.60, separated by detectable delimiters, with allowance made for the following additions:

-	F.60 fields may or may not be in the preferred order;

-	the Telex Network Identification Code (TNIC) should be preceded and succeeded by detectable delimiters:

i)	preceding delimiters are national call number and space,

ii)	succeeding delimiters are national call number, space or end of answerback (end of answerback means no more printable characters);

-	one hyphen or one space with the national call number is ignored;

-	the corresponding international access code for the "J" TNIC is:

i)	72, if the national call number consists of 5 digits,

ii)	720, if the national call number consists of less or more than 5 digits.

The international access code for all other TNICs follows Recommendation F.69. For conversion between TNICs and F.69 codes, see also Recommendation F.69.

An algorithm which meets the preceding criteria is shown in Figure 1/U.74.

FIGURE 1/U.74 (Sheet 1 of 2) - CCITT 76200

FIGURE 1/U.74 (Sheet 2 of 2) - CCITT 76210

Note 1 - Check the automatic emitting speed and wait for the end of the answerback. The answerback is considered to have ended after detection of a 300 ms period of idle.

Note 2 - "Retry" refers to another attempt to trigger the answerback.

Note 3 - Printable figures are combination No. 17 (1) to combination No. 16 (0). Spaces (combination No. 31), hyphens (combination No. 1) and equal signs (combination no. 22) are allowed in this field, but are ignored.

Note 4 - Are there one or two printable letters at the end of the answerback, preceded by a space?

Note 5 - Are there one or two printable letters following immediately the "national call number" (without space between), with space after them?

Note 6 - In the case of a letter code single "J" corresponding F.69 code is:

-	72, if the "national call number" is 5 digits long.

-	720, if the "national call number" is less or more than 5 digits.

Note 7 - Are there one or two printable letters following the "national call number", and is there no further printable character following? One space between "national call number" and network identification code is allowed.

Note 8 - Are there one or two printable letters preceding immediately the "national call number" (without space between), but with a space in front of the letter(s).

Note 9 - If unsuccessful, perform one retry after 1.5 seconds, if allowed in the protocol.

Note 10 - If answerback is not received automatically.