Talk:Transponder (aeronautics)

message: On March 15, 2007, Germany will use 7000 for VFR flights, just as the rest of Europe does, instead of 0021 and 0022. See http://www.skycontrol.net/service-providers/change-of-german-vfr-transponder-codes-ac-7000-replaces-ac-0021-and-ac-0022/ - we need to change the article accordingly
86.80.211.229 12:20, 19 February 2007 (UTC)
thread_title:  Opening heading

message: Australian procedure is to select STBY first, then select the new code, then reselect ALT, to avoid inadvertently selecting an emergency code, or another code already in use.  This is from the AIPs —The preceding unsigned comment was added by Cabdude (talk • contribs) 11:23, 1 May 2007 (UTC)
replies: text: Canadians are specifically warned not to do this, so as to not lose the protection afforded by TCAS during the code switch.  —Preceding unsigned comment added by 12.24.137.66 (talk) 14:34, 8 October 2007 (UTC)

text: I saw lately in ICAO 4444 Pans OPS a certain phraséology guideline to avoid this kind of confusion, if the controller estimates that the pilot could pass over an emergency squawk, he will use the term: RECYCLE ( put transponder on stby, the tune new code then react transponder) else he should use the term : Squawk XXX ; however with the new technology on comercial planes this is less and less a factor due to the fact that transponders are digital and no more manual inputs.  —Preceding unsigned comment added by Luckyglider (talk • contribs) 11:47, 12 May 2008 (UTC)

text: The no-standby directions in the article need to be moderated or modified.  Why do you suppose engineers designed transponders with a "standby" function?  That kind of stuff costs money and increases equipment complexity.  If it wasn't meant to be used, it would not be included.  There are many self-styled "experts" who write nonsense on various topics, since they lack proper technical grounding in the subject; this is most often evident in subjects concerning electronics and electricity, and can even include widely published authors.Having taking pilot training for several years, I can't recall a single instance of an instructor telling me not to turn the selector knob to the "standby" position, but I do remember being chided several times for failing to do so.I suggest revising the section to say that "some authorities" recommend using the standby function, while others recommend against it, and give the reasons for each.  I don't have access to the cited reference by Peppler, so I'm not prepared to pass judgment yet. —QuicksilverT @ 20:23, 1 June 2011 (UTC)
replies: text: In this case the self-styled "experts" are the engineers at Transport Canada. The Transport Canada AIM cited in the article says: "Do not select “STANDBY” while changing codes as this will cause the target to be lost on the ATC radar screen. Pilots should adjust transponders to “STANDBY” while taxiing for takeoff, to “ON” (or “NORMAL”) as late as practicable before takeoff, and to “STANDBY” or “OFF” as soon as practicable after landing. In practice, transponders should be turned on only upon entering the active runway for departure and turned off as soon as the aircraft exits the runway after landing." This seems pretty clear and the Peppler ref says pretty much exactly the same thing: "However do not select "standby" while changing codes as this action will cause the target to be lost on the radar screen at  ATC". In a recent tour of the Nav Canada Air Traffic Control Dev Center they indicated the same thing - modern computer-based radar will track a target while you change squawks on the fly, but not if you select stand-by. So, according to TC, it seems that the standby mode is there to allow the set to "idle" while on the ground and be ready for use once in the air, probably more of a carry-over from the days when they had tubes that needed to warmed up, than modern transistorized sets. If other jurisdictions have other opinions on this subject and refs can be found to show that they disagree, then this can certainly be added as "disagreement". - Ahunt (talk) 21:04, 1 June 2011 (UTC)
thread_title:  Changing squawk codes 

message: The confusion about the issue of whether TCAS II needs mode S to work or not results from the following:
In order for TCAS II to work in an aircraft, that aircraft must be equipped with at least 1 functioning Mode S transponder.
Once an aircraft is equipped, the TCAS can generate various advisories against any intruder that is equipped with an ICAO compliant transponder. In all cases, traffic advisories (TAs) can be generated. When the intruder is altitude reporting (be it Mode S or Mode C) then a Resolution Advisory (RA) is issued when necessary. When the intruder is TCAS equipped, the RAs generated are coordinated, by datalinking via the mode S transponders, to ensure that the avoiding manoeuvres are coordinated (e.g. to make sure one aircraft pitches up, and the other down, rather than both up!).
I.E. *You* have to have mode S for your TCAS to work. The intruder doesn't.
The other area of confusion about this issue is what is meant by a Mode C transponder versus a Mode A transponder. 
Mode A is an interrogation sequence that prompts the transponder to reply by encoding its identifying 4096 code.
Mode C is an interrogation sequence that prompts the transponder to reply by encoding its altitude. 
Hence, most people (and most textbooks) take the view that when an aircraft is not equipped with altitude encoding it is equipped with a Mode A rather than a Mode C transponder. This is incorrect.
ALL non mode S transponders reply to both Mode A and Mode C interrogations. ATC radars send out both a Mode A and a Mode C interrogation. When the aircraft it not equipped with Altitude reporting, the transponder still replies to the mode C call, but with a pulse frame only, and the encoded section of the reply is omitted.
I.E. 
What is popularly referred to as a 'Mode A' transponder is in fact a 'Mode A and C without Altitude Reporting transponder'.
What is popularly referred to as a 'Mode C' transponder is in fact a 'Mode A and C with Altitude Reporting Transponder'.
This incorrect designation even goes as far as many transponder controllers, where the mode selecting knob is labelled something like 'Off', 'STBY', 'A', 'A+C', when it should be 'Off', 'STBY','On', 'On+Alt'.
Nevertheless, I accept that this is a fine distinction that does not really affect a typical line pilot. However, if you want to understand how TCAS works, then it becomes an issue......
Because practically every nuance of how TCAS and Mode S function is driven by the engineering need to avoid any unnecessary transmissions in the secondary radar bands. Whereas pre-TCAS, the only transmissions were from ground radar heads to aircraft, now every aircraft is also keeping track of every other aircraft within the vicinity (something like 40 NM). Therefore, without care, the entire secondary radar bands would be swamped!
Mode S includes a lot of tricks to achieve this, but I don't propose to talk about it in this post but will expand if you wish. As far as other transponders go, appreciate that TCAS doesn't care what 4096 ident code the intruder is wearing. It only cares about the range to the intruder, and the intruders altitude. 
To find the the range, a time delay versus speed of light calculation is required. This simply needs the intruders transponder to reply, and this could be achieved by either a mode A or a Mode C interrogation.
To find the altitude, obviously a Mode C interrogation is required.
From this we can see that if TCAS sends a Mode C interrogation, it can achieve both objectives, both range and Altitude. Therefore there is no need for TCAS to send a Mode A interrogation, so to avoid garbling the secondary radar frequencies it doesn't.
I.E. TCAS only sends mode C, and not mode A, interrogations for dealing with non mode S intruders,
So, technically, TCAS will only see Mode C and Mode S transponders.
So, technically, TCAS will not see Mode A transponders, and you will not get any advisories.
However, what people think are Mode A transponders are in fact Mode A and C transponders, just without altitude encoding.
CPB
TCAS instructor
--Natasha2006 18:21, 14 June 2007 (UTC)
thread_title:  Adding a note for future reference 

message: THE STRAIGHT SCOOP ON HOW IT WORKS
by
Darryl Phillips
--Natasha2006 18:29, 14 June 2007 (UTC)
thread_title:  Mode A and Mode C 

message: 212.76.61.206: I have for a second time reverted the inclusion of mnemonics for people learning how to memorize transponder codes as part of pilot ground school. As is made very clear in Wikipedia Policy Wikipedia is not a how to manual and this information does not belong here.
As for the personal attack that went with the reversion of my edit, this is also not permitted under Wikipedia policy Wikipedia:No_personal_attacks. If you would like to discuss the issue civilly then this talk page is the forum to do that. 
- Ahunt 22:14, 1 November 2007 (UTC)
thread_title:  Deletion of mnemonics 

message: This article was tagged for consideration for merger on 11 December 2007 by PEHowland. The tag was incorrectly constructed and led to the wrong talk page, so that may have slowed down comment on this issue!
I will start off the debate by indicating that I am against merging these two articles. I don't see that they are one subject. - Ahunt (talk) 23:21, 1 January 2008 (UTC)
replies: text: Against merger - the transponder is an avionics system fitted to an aircraft, SSR is a ground based radar system. Just because the SSR interogates the transponder is not motive for one article. MilborneOne (talk) 13:08, 2 January 2008 (UTC)

text: That debate was closed four years ago. If you want to start over then you will have to re-propose it. Personally I don't see anything has changed in the intervening time. - Ahunt (talk) 00:21, 27 April 2012 (UTC)
thread_title:  Proposed merger of [[Transponder (aviation)]] with [[Secondary surveillance radar]] 

message: I have removed some unsourced information from this article on the apparent history of the term "squawk and "parrot check". Parts of this paragraph have been tagged as unreferenced for five months. The information seem doubtful or apocryphal at best and my attempts to finds refs for it have not been successful. Since no one else has found any refs for it in five months I have removed it. The response from an IP address 137.240.136.86 and 137.240.136.80 (same person) has been to edit war over it, including uncivil remarks and attempts to bully over this issue with such statements as "no one elected you sherrif (sic), move along".
The policies on this sort of issue are very clear:
"If a claim is doubtful but not harmful to the whole article or to Wikipedia, use the  tag, but remember to go back and remove the claim if no source is produced within a reasonable time."
I think five months is reasonable time.
If any one has a reference for this removed para then by all means please re-instate it. If you don't have a ref then it will remain out of the article.
For anyone who doesn't think it is important for Wikipedia to be scrupulously referenced, I suggest that you read this CBC article. A lack of references can cause real damage in some cases. - Ahunt (talk) 18:58, 13 March 2008 (UTC)
thread_title:  Unreferenced text 

message: This article should be about the item of equipment called the Transponder the large section on codes and how they are used should be deleted/moved to Secondary Surveillance Radar or similar. Any comments? MilborneOne (talk) 20:28, 7 May 2008 (UTC)
replies: text: Agree - the huge list of codes is not particularly relevant, and most examples are wrong for most of the world.
--Drpixie (talk) 06:39, 8 May 2018 (UTC)
replies: text: I see you have deleted them. Where did you move them to? - Ahunt (talk) 11:17, 27 May 2018 (UTC)
replies: text: Not moved, just deleted. The list was quite misleading - most of the codes listed only apply in specific countries. Those codes are allocated as discrete (normal) codes in the rest of the world. Pilots are required to conform to the AIP (or whatever it's called) of the country in which they're operating, so having a misleading list on wiki is something of a problem. If you need the list for some reason, it's in the history. --Drpixie (talk) 10:51, 28 May 2018 (UTC)
replies: text:  As a pilot I would not call it misleading, as each entry had the country where it was used in each capacity and circumstance. I don't think any pilot would select a code from Wikipedia and use it in the air in the wrong country based on the article. The list was a unique compilation, so I am wondering whether it should not be shifted to a new article, as suggested above. Perhaps List of aviation transponder codes or similar? - Ahunt (talk) 12:13, 28 May 2018 (UTC)
replies: text:  If you want to make such a list, your call, but personally I don't see wiki as the right place. Pilot's should be using the correct documents (AIP, AIM, etc); and a list here is instantly out of date, so interested people should be going to correct source. Perhaps a paragraph describing what codes represent (rather than a list of examples) would be more appropriate? --Drpixie (talk) 00:00, 29 May 2018 (UTC)
replies: text: Actually that is rather the point, that no AIP has a list of all the transponder codes used globally; it was a unique list. - Ahunt (talk) 01:00, 29 May 2018 (UTC)
thread_title:  Transponder codes 

message: An IP editor has now twice removed the word "not" from this sentence in the article:
"Pilots are instructed not to place the transponder in "standby mode" while changing the codes as it causes the loss of target information on the ATC radar screen, but instead to carefully change codes to avoid inadvertently selecting an emergency code."
The Transport Canada ref cited says: "Do not select “STANDBY” while changing codes as this will cause the target to be lost on the ATC radar screen."
Does anyone have any other information on this subject? Many years ago it was the practice to select "stby" when changing codes, but with radar modernization in the 1980s this was changed. 
Besides that the removal of the one word makes the sentence non-sensible. Ahunt (talk) 20:56, 7 May 2008 (UTC)
replies: text: The "standby" function mutes the transmitter, but leaves the rest of the transponder's electronics, including the timebase circuits, operating in a stable fashion.  This prevents spurious squawks from being transmitted while the code is being changed, especially on older equipment with rotary selector switches.  By leaving the circuits active, it also prevents "chirping of the timebase reference. —QuicksilverT @ 20:23, 1 June 2011 (UTC)
thread_title:  Selection of standby to change codes 

message: hI 
just some problems to find some references , i have added two SSr 3/A codes allocation but unfortunately I haven't got the latest official Icao/Nato MODE 3 allocation table however if someone could give me a hand on this this could be nice but for french paradrop I am certain of the squawks used by FR FIC also for Belgians I have no doubt over them .
have a nice day  —Preceding unsigned comment added by Luckyglider (talk • contribs) 11:41, 12 May 2008 (UTC)
thread_title:  Finding references 

message: Note to all those people who have been told by their flight instructors that the hijack transponder code of 7500 is a state secret and they are not to divulge it even under torture - that is a myth, so please stop deleting content from this article! There is no reason to remove the hijack or any other transponder code from this article. Many government websites, such as Transport Canada publish this information and it is very clearly public and not classified. See also WP:NOTCENSORED. - Ahunt (talk) 18:49, 27 January 2009 (UTC)
replies: text: Transport Canada and the FAA both disagree with you and publish the information on the internet. My own discussions with senior Transport Canada policy staff on this issue, when I was involved in the drafting of the CARs, indicate that it was never intended to be a secret and that a hijacked aircraft squawking or not squawking this code will not affect its ATC handling or other response. Any aircraft deviating from clearance and unresponsive is treated as a hijacking. The use of the code is a procedural convenience for ATC and that is all. If it were intended to be limited in the dissemination of it, it would be only taught to airline captains and not 100,000s of student pilots each year. It would also not be in every ground school text book. I specifically asked TC staff if this shouldn't be kept secret and they indicated that it should be widely disseminated as possible. They freely acknowledged that most hijackers would know about it, but that doesn't affect its use. It also doesn't put crews at risk, in many past hijackings the hijackers have asked the pilot to select 7500. You are going to have to come up with some better reason than your opinion "I believe it is in the best interest of the aviation community to limit where this code is published" to delete it from the article. - Ahunt (talk) 20:31, 15 May 2009 (UTC)

text: I flew helicopters too for several decades and what you have written is ill-informed. Read the thread above. - Ahunt (talk) 02:48, 1 April 2010 (UTC)

text: Read the section above where I discuss the Transport Canada opinion on this subject. TC insists that disseminating the information as widely as possible puts no one at risk. Despite your insistence that Wikipedia be censored, Wikipedia is not censored. Your continued attempts to censor Wikipedia against consensus here and official government policy that this information be widely distributed is misguided personal opinion. - Ahunt (talk) 23:13, 1 April 2010 (UTC)
replies: text: Actually, there's no clear concensus to remove the code from the article, your own multiple posts not withstanding. If TC doesn't have a problem with it, why should we? - BilCat (talk) 06:23, 17 May 2010 (UTC)
replies: text: Bill is quite right: Not only is there no consensus to delete this information, but the publication of this information as "unclassified" by TC and the FAA just proves that your fears and prejudices are unfounded. Removing this text is nothing more than censorship. - Ahunt (talk) 12:35, 17 May 2010 (UTC)
replies: text: I knew about this code when I was nine years old. Not only is Wikipedia not censored, removing it is, in a word, silly. - The Bushranger Return fireFlank speed 13:51, 17 May 2010 (UTC)
replies: text: I am a commercial pilot and flight instructor.  I fly approximately five days a week and I always find it funny when someone acts like the 7500 code is something other than public information.  As a private, commercial, or airline transport pilot you are not privy to ANY classified or secret information (on any level) because of your license.  To believe that you are is simply misinformed, arrogant, and setting yourself up to be the butt of a good few jokes at the airport lounge.  The part of all this which was sad and not funny at all, was that because one individual thought he was entitled to knowledge that he felt others should not be entitled to, he was editing the article despite the consensus that the information should have stayed.  One person's ignorance was preventing others from becoming educated on the fact.  I'm glad we were talking about something as simple as a transponder code that is rarely used; I hope that guy doesn't behave that way when more important knowledge is involved.  — Preceding unsigned comment added by 173.81.159.193 (talk) 00:45, 28 September 2011 (UTC)
replies: text:  - Ahunt (talk) 11:39, 28 September 2011 (UTC)

text: The editnotice doesn't seem to have been moved to match the article itself. --SoledadKabocha (talk) 02:00, 19 February 2015 (UTC)

text: *The template page has now been moved. Anthony Appleyard (talk) 08:46, 19 February 2015 (UTC)
thread_title:  Deletion of hijack code 7500 

message: There seems to have been an attempt last February to move the Transponder Modes section into a main article.  The section in this article has since grown considerably.  I have flagged the page proposing a move of the section to the Aviation_transponder_interrogation_modes article.  A summary of the section, moving the text over, and a format check will have to be done.  Given the size of the section, I believe it deserves its own article.--Fbfree (talk) 05:37, 6 August 2009 (UTC)
replies: text: Check a summary provided in Secondary_surveillance_radar#Modes.  This doubling up may need reconciliation.  Perhaps the listing of mode types should only be provided in the main article. --Fbfree (talk) 05:57, 6 August 2009 (UTC)
replies: text: Sounds like a good move to me. it will reduce overlap and also some clutter in this article. - Ahunt (talk) 00:58, 8 August 2009 (UTC)

text: I checked over what you did on all three articles and it looks good - I agree that there isn't much point leaving a short section there. - Ahunt (talk) 18:30, 8 August 2009 (UTC)
thread_title:  Move "Transponder modes" section 

message: I am not aware of the actual numbers involved, but the number of less than 4096 available squawk codes looks a bit low. How does ATC avoid assigning the same code to two aircrafts at the same time that might then fly into the same airspace?--Cancun771 (talk) 17:17, 23 December 2009 (UTC)
replies: text: There are four Mode 3 digits available and you can select 0-7 on each digit, which gives (8X8X8X8) 4096 combinations, including ones that can't be assigned for daily use, such as 0000, 7500, etc. In many cases aircraft are assigned the same code in the same airspace, such as 1200 for transiting VFR traffic. Otherwise codes are assigned from a computer database list for each locality to avoid duplication of codes in the same airspace when that is required. - Ahunt (talk) 23:54, 1 April 2010 (UTC)
thread_title:  Avoidance of dual code assignment 

message: The introduction of a table for US transponder codes has made a bit of a mess of the article. There are still US codes in the second section and the two sections should probably both be put into table format, or else neither. - Ahunt (talk) 00:18, 27 April 2012 (UTC)
replies: text: I agree.  I think that including the codes at all on this page is excessive and unnecessary.  Why not just reference the documents where the assignments can be found, and be done with it? Conortodd (talk) 00:12, 10 May 2012 (UTC)
replies: text: That makes some sense. I think a list of commonly used codes is okay, but the formatting needs to be better than it is right now. - Ahunt (talk) 11:45, 10 May 2012 (UTC)
replies: text: In reading over the information and the refs I think the best solution is to combine both into the existing table. At least this will eliminate duplication and the US-centric look to the article right now. Let me give it a try over several edits and then see how it looks. - Ahunt (talk) 15:51, 10 May 2012 (UTC)
replies: text: Okay, I have combined them. See if that at least makes some sense now. - Ahunt (talk) 19:53, 10 May 2012 (UTC)
replies: text: That looks dandy.  I hope they pay you well :) Conortodd (talk) 18:53, 18 May 2012 (UTC)
replies: text: Glad you think that looks better. It's all free! - Ahunt (talk) 19:12, 18 May 2012 (UTC)
replies: text: Ahunt and whomever else is interested, what about changing "to" to a dash "-".  I am not sure there is a standard here but to me it sould look a bit better and flow a little better.  Just wanted to get your oppinion.  You did a really good job on it, by the way.ErikkFriberg (talk) 13:09, 5 December 2012 (UTC)
replies: text:  - Ahunt (talk) 13:57, 5 December 2012 (UTC)
thread_title: Table

message: From "Navigating  the DC SFRA
Effective 0500 Z, 02/17/2009"
http://www.leesburgva.gov/Modules/ShowDocument.aspx?documentid=223
also http://tfr.faa.gov/save_pages/detail_1_6386.html
6.      Keep your discrete code to the ground.  squawking 1200 for as little as ten 
seconds while in SFRA airspace will result in an FAA violation !!!! 
7.      Never squawk 1200 in SFRA !!!!  — Preceding unsigned comment added by Wamnet (talk • contribs) 20:36, 18 June 2012 (UTC)
thread_title:  SFRA rules on squawking 1200 

message: In past it was used for Air Force One, no? Flightsoffancy (talk) 16:47, 10 August 2012 (UTC)
replies: text: It isn't listed in any of the refs cited in the article either way. Do you have a reference? - Ahunt (talk) 23:09, 10 August 2012 (UTC)
replies: text: If 0001 use was abandoned then current refs wont show it.  This site lists 0001 as "0001: Military code for high speed uncontrolled (non ATC directed) flight (US)", which could be Air Force One, but that is speculative. This site note 0000 used for drones , which article does not mention.  I am beginning to think 0001 for AF1 is just "hangar talk" and not current policy (although it might have in distant past). Flightsoffancy (talk) 16:49, 13 August 2012 (UTC)
thread_title:  0001 no longer in use? 

message: "Around busy airspace there is often a regulatory requirement that all aircraft be equipped with an altitude-reporting mode C or mode S transponders. In the United States, this is known as a Mode C veil."
I think there should be a difference distinguished between the Mode C Veil and Class B and C transponder (Mode C) requirements.  This is with the understanding that the Mode C Veil and Class B airspace are almost the same airspace, but there is a slight difference.  Look at DFW, you can be in the Mode C Veil in some places but not in Class B, and on the flip side, you can be in class B but not in the Mode C veil.  I know this is nit picking but that what the FAA does.
I feel it should be distinguished, but I just wanted to see what others thought. 
--ErikkFriberg (talk) 15:19, 4 December 2012 (UTC)
thread_title:  "Operation" 

message: This information is missing and would be a beneficial inclusion at the top of the article.  — Preceding unsigned comment added by 68.97.65.236 (talk) 16:54, 12 July 2016 (UTC)
thread_title:  Invention and Earliest Adoption for Use 

message: Noticed that this article still references AIM RAC for transponder operation whereas it is now covered in COM.Dwt2 (talk) 22:40, 29 July 2016 (UTC)
thread_title: AIM References

message: Hello fellow Wikipedians,
I have just modified 2 external links on Transponder (aeronautics). Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:
*Added archive https://web.archive.org/web/20100709182349/http://www.tc.gc.ca/eng/civilaviation/publications/tp14371-rac-1-0-474.htm to http://www.tc.gc.ca/eng/civilaviation/publications/tp14371-rac-1-0-474.htm
*Added archive https://web.archive.org/web/20090124120704/http://www.caa.co.uk/docs/64/DAP_ACD_14_SSR_Transponder.pdf to http://www.caa.co.uk/docs/64/DAP_ACD_14_SSR_Transponder.pdf
When you have finished reviewing my changes, you may follow the instructions on the template below to fix any issues with the URLs.
Cheers.—InternetArchiveBot (Report bug) 02:25, 26 January 2018 (UTC)
thread_title:  External links modified (January 2018) 

message: Was there any sort of consensus over deleting the vast majority of this article? Most editors seemed to have no problem with it, especially since discussion has been about allowing a specific code on the list. I'm going to revert for now.  — Preceding unsigned comment added by 73.65.146.100 (talk) 18:06, 11 June 2018 (UTC)
replies: text: Most of the table is american-centric so I think it should be cut down just to show the ones that are standard worldwide only (7000, 7500, 7600, 7700 ) although I believe they should actually be on the SSR page or similar not on a page that describes the equipment rather than the "system" it is used in. MilborneOne (talk) 10:49, 15 June 2018 (UTC)
replies: text: As I argued above, I am in favour of retaining the table, either in this article or a new list article. I would have started the new list article, but that will depend on the outcome of this discussion. - Ahunt (talk) 15:11, 15 June 2018 (UTC)
replies: text: Ahunt, it seems the consensus is to retain the table in another page. Do you want to move it? If not, I will. Perhaps we keep reference to the very few standard codes that are used everywhere (7700, 7600, 7500) and put the rest is a List of Transponder Codes page that make it clear these are local and/or historic codes. --Drpixie (talk) 02:29, 15 July 2018 (UTC)
replies: text: That sounds like a good approach. Please do go ahead, if you have the time this weekend! - Ahunt (talk) 12:50, 15 July 2018 (UTC)
replies: text: Done, with some rewording --Drpixie (talk) 11:39, 16 July 2018 (UTC)
thread_title:  Deletion of Table 

message: The article mentions frequency units for listening and replying, but not for the transponder frequency itself. Maybe it is somehow obvious to an involved person, but I find it unhelpful that I don't know if it's mHz, kHz or what.
francesco3 (talk) 14:38, 29 October 2019 (UTC)
replies: text: The lead says "The transponder receives interrogation from the Secondary Surveillance Radar on 1030 MHz and replies on 1090 MHz" these are the only frequencies involved. MilborneOne (talk) 14:43, 29 October 2019 (UTC)
thread_title:  Missing frequency units 

message: Hi. The article needs clarification discussing the general conspicuity code situation in UK airspace. There are now two codes for conspicuity: 7000 for VFR and now 2000 for IFR. One is told 'squawk conspicuity' by ATC as required and it is then up to the pilot to choose the appropriate code  https://andrewsaviation.co.uk/uk-caa-squawk-a-change-to-rft-phraseology/   — Preceding unsigned comment added by Longfinal (talk • contribs) 15:30, 11 May 2021 (UTC)
thread_title:  UK: use of conspicuity codes 

message: The inventor of the Highjack Code was a Royal Air Force (RAF) Radar Technician who was at RAF Bishops Court, Northern Ireland, working on the RAF's first solid state Secondary Surveillance Radar.  He was assisted by a Sergeant technician who helped test and write up the invention.  The symbol on the ground radar scope was a combination of the symbols for Emergency 7700 and loss of Communications 7600.  In June 1973 both were awarded £20 and a RAF Strike Command Certificate of Merit, from Air Chief Marshal Andrew Humphrey in recognition of their initiative and inventiveness towards the improvement of engineering services.  They also received a congratulatory letter from Air Commodore E W Wooten CBE, DFC AFC, MBIM, RAF, who was Military Air Traffic Operations. He said in his letter that it was an excellent proposal and had  made a contribution to air safety. 78.144.187.141 (talk) 15:36, 4 August 2023 (UTC)
replies: text: Fascinating story. Got a reference that says that or is it WP:OR? - Ahunt (talk) 15:49, 4 August 2023 (UTC)
thread_title:  Secondary Surveillance Radar for HighJack Code - Inventor