Publication: Magyar Közlöny
Issue: MK-2009-104 (Year: 2009, Number: 104)
Era: 2004-2010
Section: 
Paragraph Index: 1956

c) the composition of prefixes within a 15 character maximum. Note.— By agreement between the administrations concerned, it is permissible for supervisory signals to contain a station identification prefix using characters selected from columns 4 through 7 of IA-5. 8.6.3.3.2 Recommendation.— For multipoint implementations designed to permit only centralized (computer-toterminal) operations, the provisions of 8.6.3.7 should be employed. 8.6.3.4 BLOCK CHECK CHARACTER 8.6.3.4.1 Both system category A and B shall utilize a block check character to determine the validity of a transmission. 8.6.3.4.2 The block check character shall be composed of 7 bits plus a parity bit. 8.6.3.4.3 Each of the first 7 bits of the block check character shall be the modulo 2 binary sum of every element in the same bit 1 to bit 7 column of the successive characters of the transmitted block. 8.6.3.4.4 The longitudinal parity of each column of the block, including the block check character, shall be even. 8.6.3.4.5 The sense of the parity bit of the block check character shall be the same as for the information characters (see 8.6.1.2.3). 8.6.3.4.6 SUMMATION 8.6.3.4.6.1 The summation to obtain the block check character shall be started by the first appearance of either SOH (start of heading) or STX (start of text). 8.6.3.4.6.2 The starting character shall not be included in the summation. 8.6.3.4.6.3 If an STX character appears after the summation has been started by SOH, then the STX character shall be included in the summation as if it were a text character. 8.6.3.4.6.4 With the exception of SYN (synchronous idle), all the characters which are transmitted after the start of the block check summation shall be included in the summation, including the ETB (end of transmission/block) or ETX (end of text) control character which signals that the following character is the block check character. Annex 10 — Aeronautical Communications Volume III 22/11/07 I-8-8 8.6.3.4.7 No character, SYN or otherwise, shall be inserted between the ETB or ETX character and the block check character. 8.6.3.5 DESCRIPTION OF SYSTEM CATEGORY A System category A is one in which a number of stations are connected by a multipoint link and one station is permanently designated as the control station which monitors the link at all times to ensure orderly operation. 8.6.3.5.1 LINK ESTABLISHMENT PROCEDURE 8.6.3.5.1.1 To establish the link for transmission, the control station shall either:

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