SECURITY WARNING (FORMAT LINE 4). -A security warning is the first component of format line 4. The appropriate operating signal (ZNR or ZNY) will always be followed by a classification character repeated five times. The operating signal and classification characters are as follows:

ZNR UUUUU -For off-line encrypted messages and classified messages transmitted in the clear;

ZNY EEEEE -For unclassified EFTO messages; and

ZNY, followed by CCCCC, SSSSS, or TTTTT -For Confidential, Secret, or Top Secret messages, respectively.

For SPECAT and SPECAT SIOP-ESI messages, the five redundant security characters are followed by an oblique (/) AAAAA for SIOP-ESI or BBBBB for all other SPECAT messages. For example, format line 4 for a Top Secret SPECAT message would be:

ZNY TTTTT/AAAAA(2CR, 1LF)

END OF MESSAGE (EOM) (FORMAT LINES 15 AND 16). -Format line 15 is the EOM validation line that is used to inhibit suspected straggler messages. Format line 15 consists of the SSN in format line 2

preceded by the number sign (#). Format line 16 consists of the EOM functions. The EOM functions consist of normal teleprinter ending procedure when five-level Baudot code is used (2CR, 8LF, 4Ns, 12LTRS). However, for ASCII, 12 delete functions are used (12DEL). The EOM for the message with format line 2 shown in figure 1-2 would be as follows:

Position 34 through end-of-routing signal (start-

Format lines 1, 2, 4, and 5 must all be accurately prepared. Backspacing, lettering out, double-spacing, or using two or more FIGURES and LETTERS functions in sequence will cause the ASC to reject the message during attempted transmission from the originating station. The EOM validation appearing in format line 15 and the EOM function in format line 16 must be prepared in uninterrupted sequence, be letter-perfect, and be without corrections.

General Teleprinter Rules

A leader must precede the header to ensure acceptance and transmission of the first character of the message header. The leader for the five-level Baudot code (most common) consists of at least six blanks and six letter functions. The leader for the ASCII (eight-level Baudot code) consists of at least six nulls and six delete functions. This will ensure acceptance and transmission of the first character of the message header.

When a message is assigned dual precedence, the higher precedence is shown in format line 2 (position 1). Both precedences are shown in format line 5.

Communications personnel of tributary stations must ensure that a record is made of the time of file (TOF) and the time available for delivery (TAD). These times are used to determine message-processing times.

Message Lengths

Messages cannot exceed more than 20 lines of heading and text, beginning with format line 5. Messages that exceed the 20-line limit must be divided into pages for transmission. The second and succeeding pages of a message are identified by the page number, the routing indicator of the station of origin, and the SSN. The security classification of classified messages follows the page identification. After the first letter of the classification, you must separate each letter by one space from the previous letter. For example:

On unclassified messages, "UNCLAS" is placed after the page identification with no spaces separating the letters.

^{When a message exceeds five textual pages, the} message must be divided into transmission sections. The message should be separated at a convenient point on the last permissible page of a transmission section. This normally will be at the end of a sentence or _{cryptopart. Each section must be numbered in plain} language at the beginning of the text following the classification or abbreviation "UNCLAS." For ^example:

UNCLAS SECTION 1 OF 2

In long encrypted messages, when a transmission section starts with a new cryptopart, the designation of the cryptopart follows the designation of the transmission section. Also, when a numerical group count is associated with an off-line encrypted message and is indicated in format line 10, the count must ^{indicate the number of groups in the textual section being transmitted- not the number in the complete} message. Cryptopart identification is included in the group count; the page identification and transmission _{section are not.}

Statistical and meteorological messages can have _{up to 100 lines of text without paging when the inclusion of paging information would disrupt processing by the user. However, you should divide} these types of messages into transmission sections if they exceed 100 lines of text.