Publication: Magyar Közlöny
Issue: MK-2009-104 (Year: 2009, Number: 104)
Era: 2004-2010
Section: 
Paragraph Index: 2291

b) the starting of the B-timer. 3.1.2.6.11.4.2 Extraction. To extract the broadcast message, an interrogator shall transmit RR equals 16 and DI not equal to 7 or RR equals 16 and DI equals 7 with RRS equals 0 in a subsequent interrogation. 3.1.2.6.11.4.3 Expiration. When the B-timer period expires, the transponder shall clear the DR code for this message, discard the present broadcast message and change the broadcast message number (from 1 to 2 or 2 to 1) in preparation for a subsequent Comm-B broadcast. 3.1.2.6.11.4.4 Interruption. In order to prevent a Comm-B broadcast cycle from delaying the delivery of an air-initiated Comm-B message, provision shall be made for an air-initiated Comm-B to interrupt a Comm-B broadcast cycle. If a broadcast cycle is interrupted, the B-timer shall be reset, the interrupted broadcast message shall be retained and the message number shall not be changed. Delivery of the interrupted broadcast message shall recommence when no air-initiated Comm-B transaction is in effect. The message shall then be broadcast for the full duration of the B-timer. 3.1.2.6.11.4.5 Enhanced broadcast Comm-B protocol. A broadcast Comm-B message shall be announced to all interrogators using II codes. The message shall remain active for the period of the B-timer for each II code. The provision for interruption of a broadcast by non-broadcast Comm-B as specified in 3.1.2.6.11.4.4 shall apply separately to each II code. When the B-timer period has been achieved for all II codes, the broadcast message shall be automatically cleared as specified in 3.1.2.6.11.4.3. A new broadcast message shall not be initiated until the current broadcast has been cleared. Note.— Due to the fact that broadcast message interruption occurs independently for each II code, it is possible that the broadcast message timeout will occur at different times for different II codes. Annex 10 — Aeronautical Telecommunications Volume IV 22/11/07 3-40 3.1.2.7 EXTENDED LENGTH COMMUNICATION TRANSACTIONS Note 1.— Long messages, either on the uplink or the downlink, can be transferred by the extended length message (ELM) protocols through the use of Comm-C (UF = 24) and Comm-D (DF = 24) formats respectively. The ELM uplink protocol provides for the transmission on the uplink of up to sixteen 80-bit message segments before requiring a reply from the transponder. They also allow a corresponding procedure on the downlink. Note 2.— In some areas of overlapping interrogator coverage there may be no means for coordinating interrogator activities via ground communications. However, the ELM communication protocols require more than one transaction for completion; coordination is thus necessary to ensure that segments from different messages are not interleaved and that transactions are not inadvertently closed out by the wrong interrogator. This can be accomplished through the use of the multisite communications protocols or through the use of the enhanced ELM protocols. Note 3.— Downlink extended length messages are transmitted only after authorization by the interrogator. The segments to be transmitted are contained in Comm-D replies. As with air-initiated Comm-B messages, downlink ELMs are either announced to all interrogators or directed to a specific interrogator. In the former case an individual interrogator can use the multisite protocol to reserve for itself the ability to close out the downlink ELM transaction. A transponder can be instructed to identify the interrogator that has reserved the transponder for an ELM transaction. Only that interrogator can close out the ELM transaction and reservation. Note 4.— The multisite protocol and the non-selective protocol cannot be used simultaneously in a region of overlapping interrogator coverage unless the interrogators coordinate their communications activities via ground communications. 3.1.2.7.1 COMM-C, UPLINK FORMAT 24 UF RC NC MC AP The format of this interrogation shall consist of these fields: Field Reference UF uplink format 3.1.2.3.2.1.1 RC reply control 3.1.2.7.1.1 NC number of C-segment 3.1.2.7.1.2 MC message, Comm-C 3.1.2.7.1.3 AP address/parity 3.1.2.3.2.1.3 3.1.2.7.1.1 RC: Reply control. This 2-bit (3-4) uplink field shall designate segment significance and reply decision. Coding RC = 0 signifies uplink ELM initial segment in MC = 1 signifies uplink ELM intermediate segment in MC = 2 signifies uplink ELM final segment in MC = 3 signifies a request for downlink ELM delivery (3.1.2.7.7.2) 3.1.2.7.1.2 NC: Number of C-segment. This 4-bit (5-8) uplink field shall designate the number of the message segment contained in MC (3.1.2.7.4.2.1). NC shall be coded as a binary number. Chapter 3 Annex 10 — Aeronautical Telecommunications 3-41 22/11/07 3.1.2.7.1.3 MC: Message, Comm-C. This 80-bit (9-88) uplink field shall contain:

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