# Auto Alarm Actuation



## Shipbuilder (Jun 30, 2005)

Does anyone remember how many four second dashes were required to set off an auto alarm? 
Bob


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## wsrmb01 (May 24, 2020)

I'm sure it was 4 x 4 second dashes, separated by 1 sec.
Had occasion to use it once near Santos, Brazil, but I sent 6 by hand, as 1st mate was getting anxious!
..from website ....http://alt.g4gbp.co.uk/kit.html
The Auto-Alarm was always on watch during the times that the Radio Officer was not.
It was tuned to one frequency - 500kHz to listen for Auto-Alarm distress signals. The Auto-Alarm distress signal was transmitted as twelve, four second dashes spaced by one second. The Auto Alarm would listen and when a signal was received would start to time. If it received a 4 second dash it would then go on to look for the next and so on. Any time it received four, four second dashes it would ring the bells to alert the Radio Office that there was a distress in progress. If the second, or subsequent signals proved not to be the correct sequence of four second dashes, the unit reset itself.


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## Harry Nicholson (Oct 11, 2005)

I need to go back 60 years - but I recall it was 4x4 second dashes at 1 sec spacing. Here's what I wrote in a memoir of the time:
From: 'You'll See Wonders" . . . "At the end of the watch I'll set up the Auto-Alarm, a safety device carried by all ship's stations. Unattended, that grey box filled with relays will listen on the Distress Frequency for a series of four-second dashes, each dash followed by a one-second space. If the magic box detects a sequence of four dashes of correct spacing, it will ring a bell in my cabin and another on the bridge. It's a loud bell, sited on the bulkhead just a couple of feet from my ear when I'm in my bunk. The clapper is sometimes bent back by some irritated chap to render it less fierce. An old sock would subdue the beast — but that would be illegal. When the bell sounds, I'll roll out of bed and stagger up to the wireless room in pyjamas. Not so bad on calm nights, but no fun when she is pitching in the teeth of a soaking monsoon. The trouble is, occasional bursts of static can mimic that alarm signal. There are far more false alarms than real distress calls; static-prone tropical waters can leave a radio man short of sleep."

The memoir has just appeared. The title comes from advice given when I went to sea: brother-in-law, an engineer with Elder Dempster, cautioned me to never be cynical - 'You'll see wonders', he said. 'You'll See Wonders' is the sequel to my first memoir, 'The Best of Days'. It has been a pleasurable two years in the writing, and I've enjoyed trying to write with the spirit and atmosphere of the time. It is not autobiography, but memoir - which allows for scenes and character to be built where memory gives only snatches and fragments of conversation and visual recall of sixty years ago. I'm now cogitating around a possible book 3, whilst Pieris rapae is out there, in the sunshine, laying her little lime-green eggs on my cabbages. The cover of "You'll See Wonders" is from one of the last paintings by my old friend and venerable man of the sea, Bill Wedgwood of Robin Hood's Bay - he did it for the book. Though he did not see it finished, I passed him chapters as they emerged.

I do hope I've got it right. It's a pain to make changes once the bird has fledged.


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## Shipbuilder (Jun 30, 2005)

Thanks, I seem to have pretty firm memories of only three being needed to set it off, but probably false memories. That is why I didn't mention any number when asking the question - Didn't want to plant seeds of doubt when answering the question. I also used it once at 2230 gmt off the trade routes, and it got loads of responses, and the nearest ship was standing by us within three hours, but we didn't need to abandon (fire) - Three days drifting with _Overseas Argonaut _standing by, and then towed to Dakar with salvage tug for one month of repairs in Dakar -


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## trotterdotpom (Apr 29, 2005)

Pre


Shipbuilder said:


> Thanks, I seem to have pretty firm memories of only three being needed to set it off, but probably false memories. That is why I didn't mention any number when asking the question - Didn't want to plant seeds of doubt when answering the question. I also used it once at 2230 gmt off the trade routes, and it got loads of responses, and the nearest ship was standing by us within three hours, but we didn't need to abandon (fire) - Three days drifting with _Overseas Argonaut _standing by, and then towed to Dakar with salvage tug for one month of repairs in Dakar -


Pretty sure four four second dashes were required to activate most auto alarms, Shipbuilder, but you've got me wondering now. I sailed on Overseas Argonaut in '79 - glad to hear they looked after you. A month in Dakar would have been a laugh!

John T


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## Shipbuilder (Jun 30, 2005)

trotterdotpom said:


> Pre
> 
> 
> Pretty sure four four second dashes were required to activate most auto alarms, Shipbuilder, but you've got me wondering now. I sailed on Overseas Argonaut in '79 - glad to hear they looked after you. A month in Dakar would have been a laugh!
> ...


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## Shipbuilder (Jun 30, 2005)

Thanks John,
For me, Dakar was pretty awful. All the repair radio traffic had to go via our satellite, as they didn't want to use the agent. So I was at it from 0800 in the morning to about 2200 at night, enormous repair lists etc. I was allowed out for 20 minutes per meal at first, but when things calmed down, I wasn't confined to the radio room as much. Also, all the crew got freebie satellite calls home once a week that was easy enough, but still time consuming. Just keeping up with the radio accounts was a mammoth task. At weekends, I could usually have half a day off on Sunday, and go to a local hotel for the afternoon. I could have flown home with the rest of them, but not paticularly keen on flying, so remained there so my opposite number could have Christmas at home. On completion of repairs, instead of going back the to UK, our original destination, we returned to the Cape, so in effect, when we got back, I had done two trips in a row (4 months), so consequently got four months off at the end of it, which was great, and worth all the discomfort of Dakar. 
A very intersting experience -


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## Ron Stringer (Mar 15, 2005)

Back in the 1950s a common PMG question required you to draw an auto alarm and describe how it registered an Alarm signal and actuated the alerting bells. Hatches, pawls and cams featured strongly.


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## wsrmb01 (May 24, 2020)

I also originally thought that the Auto-Alarm Eqpt only required 3 * 4 sec dashes. Perhaps there were different 'models' floating about!


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## Shipbuilder (Jun 30, 2005)

The Siemens SB2182 selector was a mass of relays, and describing the action was very complicated, I dreaded it coming up in the exam, but they just asked about what happened in the event of power failure, that was quite easy! . The auto alarms I sailed with were AEI, Marconi, Redifon, Kelvin Hughes, and ITT, but I always thought they only required three dashes!


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## trotterdotpom (Apr 29, 2005)

Shipbuilder said:


> Thanks John,
> For me, Dakar was pretty awful. All the repair radio traffic had to go via our satellite, as they didn't want to use the agent. So I was at it from 0800 in the morning to about 2200 at night, enormous repair lists etc. I was allowed out for 20 minutes per meal at first, but when things calmed down, I wasn't confined to the radio room as much. Also, all the crew got freebie satellite calls home once a week that was easy enough, but still time consuming. Just keeping up with the radio accounts was a mammoth task. At weekends, I could usually have half a day off on Sunday, and go to a local hotel for the afternoon. I could have flown home with the rest of them, but not paticularly keen on flying, so remained there so my opposite number could have Christmas at home. On completion of repairs, instead of going back the to UK, our original destination, we returned to the Cape, so in effect, when we got back, I had done two trips in a row (4 months), so consequently got four months off at the end of it, which was great, and worth all the discomfort of Dakar.
> A very intersting experience -


Sounds like murder and then listening to everyone telling you that you did nowt!
I recall meeting quite a few nice French folk and also getting chased round Dakar by a gang of shoe shine boys. They won! 

John T


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## Shipbuilder (Jun 30, 2005)

They were OK in Dakar Marine. We never had anything locked up and nothing was stolen. It was very hot and the AC was off all the time. When we went to the hotel swimming pool on Sunday afternoons, there was usually a group of us, so no trouble there, but I was glad to leave -


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## R651400 (Jun 18, 2005)

The Mimco Type M Auto Alarm and am sure its Seaguard successor had the same selector unit which required four x four second dashes spaced by one second intervals to be properly activated...
Draw the circuit and explain the action of said same AA selector unit was a favourite PMG theory paper quedstiom of the day.


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## Baulkham Hills (Jul 11, 2008)

I sailed with the Marconi Seaguard on one ship, it was a magnificent piece of machinery, it had a spinning weight, which was started by hand when turning on and plenty of cams. Not too sure how it worked. But down in West Africa with heavy static it would merrily register the what was static as a 4 second dash, and every so often like some demented poker machine it would pluck the magic four 4 second dash from the static set off the auto alarm and poor old sparky would struggle up to the radio room listen in 500 kc/s to listen to heavy static for a while, I don't believe it would have registered a genuine 4 second dash in such heavy static. The Lifeguard was a mass of valves but much better. Never really had breakdown problems with either.


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## Troppo (Feb 18, 2010)

I had to draw a block diagram of a lifeguard N for my theory exam.

After having done it hundreds and hundreds of times coming on and going off watch - it was 4 dashes...mind you, I had to think about it for a bit.



I always used the AKD to test the AA.


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## trotterdotpom (Apr 29, 2005)

#15. "I always used the AKD to test the AA. "

Me too. the boogie woogie clicking and ticking on the Marconi one got my foot tapping.

That Seaguard auto alarm had to be started by spinning a little doo dah metal thingy at the top of the panel. I always thought, this won't work but it always did. The electronic ones were just as bad with static, I always thought.

John T


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## R651400 (Jun 18, 2005)

The selector unit of Mimco Type M and Seaguard AA indeed was an electro-mechanical work of art.
The action depended on a synchronous motor whose frequency was provided in Type M by a vibrating reed and Seaguard I believe valve oscillatory wizardry.
The spindle started the centrifugal action of the selector motor and if it should stopp when "en garde" the centrifugal weight dropped closing the "motor stopped" contacts thence activating the alarm bells..
Only sailed with Type M and never encountered heavier QRN than Singapore/Surabaya/Sydney run particularly during the North Australian "wet" and the AA selector whizzed and whirred continuously yet I don't recall many if any false alarms.









Type M.jpg


Mimco Type M Auto Alarm 1950's




www.shipsnostalgia.com


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## Ron Stringer (Mar 15, 2005)

Sailed with the Type-M (_Vigilant_) auto alarm on several ships. It always managed to raise eyebrows on fellow crew members if they saw me setting it to work when I was going off watch. The vibrating reed had to be set in motion by means of giving a sharp blow to the side of the cabinet, while at the same time it was necessary to depress and spin the spring-loaded knob on the front panel (so as to engage its spindle with a gear on the motor shaft). Hopefully the combined stimulus was sufficient to spin the motor and supply it with the right frequency and level of pulses of energy required to keep it running. Often required several attempts to co-ordinate the movements and apply enough force to set things running. When I explained that it was absolutely necessary to bang on the equipment cabinet to make the thing work, the disbelieving looks on the faces of the onlookers were always a source of amusement. You could see their minds associating my actions with their Dads' treatment of the early unco-operative TV receivers.


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## gwzm (Nov 7, 2005)

Three consecutive correctly timed dashes would trigger the alarm. Still have a mental image of the Marconi autoalarm and the three latches in series to trigger it.

Happy days
gwzm


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## gordonarfur (May 27, 2018)

All the ships i sailed on were fitted with marconi auto alarm equipment. Even the Union Steamship Co of NZ had them and the qrn at times in the South Pacific around NZ and the islands at times was an absolute pest. I would be in and out of my bunk every few minutes then tearing up to the radio room to listen to an earful of static.


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## phdad (Sep 5, 2019)

Shipbuilder said:


> Does anyone remember how many four second dashes were required to set off an auto alarm?
> Bob


ITU rules dictate he leaves a receiver tuned to 500 kc with a decoder attached - if that decoder hears at least four 4-second dashes each with 1-second seperation, relays in the decoder will clamp shut triggering alarm bells in the radio room, in the radio officer's sleeping quarters, and up on the bridge, to warn of a distress message about to be sent on 500 kc.


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## Baulkham Hills (Jul 11, 2008)

As noted four 4 second dashes would activate the A/A but the autokey would actually send twelve 4 second dashes with one second spacing followed by SOS (3 times ) followed by de and callsign (3 times). Then the actual distress message.If the AKD was not manually stopped it would go on for 36 hours of course without the distress message. A coast station could send it as well or another ship close by. Sometimes the A/A would go into alarm especially at night and it would be a coast station in Canada and you would be rounding the Cape.I think generally coast stations would take over the distress and co-ordinate the rescue. Silence periods would still be observed but the station involved would still send the twelve 4 second dashes and an updated distress message proceeded by SOS.Every message pertaining to the distress was proceeded by SOS and the recommended speed was 12 words per minute. I still practically fall out of my chair when i hear an SOS sent in some old movie, a bit like Pavlov's dog I suppose. Normal working was supposed to move to 512 kc/s but this was in theory because ships out of range of distress reception would go merrily calling until the QRT distress was sent in a very stern manner.
On occasion in a dead part of the world radio wise some one would check that the AKD was actually keying the emergency transmitter and not stop it until well past the 4th dash then realized that they were actually starting a distress call then it would abruptly stop followed by total silence, For all it's faults it was a very good system in the days before Satellite communication, I personally was not impressed with GMDSS and I generally found the person responsible for it, had very little knowledge or interest in it. When I left the radio room I never wanted anything more to do with GMDSS. On occasion when I was called to make it work it was usually operator error. Even as it was introduced I felt it was a poorly conceived concept. But that's my opinion.(to quote Mandy Rice Davis "he would say that")
While not a big fan of Marconi Marine equipment (especially their radars) I must pay complement to their a/a and akd being robust and reliable.


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## djringjr (Feb 11, 2008)

Shipbuilder said:


> Does anyone remember how many four second dashes were required to set off an auto alarm?
> Bob


I would guess that both were correct for different time periods, I'm guessing after 1959 when "Electronic Commuication" by Robert L. Shrader (W6BNB) was first published there was a change in the number of dashes, because even the 1991 6th edition says "three dashes" - it's obvious from comparing this with other publications and the bizarrely worded FCC regulations that Mr. Shrader (a dear friend of mine who died at his 99th year on April 11, 2012, who edited his book brilliantly never new about the change from 3 correct dashes to 4 correct dashe

From "MARINE RADIOTELEGRAPH OPERATOR LICENSE HANDBOOK" by Edward. M. Noll, 1975, 1st Edition, 1st Printing, copyright Howard W. Sams & Co., Inc.

From page 27:

The standard autoalarm signal involves the transmission of four-second pulses with intervening one-second spaces for a period of one minute. Thus twelve pulses are transmitted in a one-minute period. Autoalarm receivers must respond to four successive pulses of this type, setting off the alarm bells.

Ed Noll cites the FCC regulations in this book as being the edition of FCC Part 83 as of March 7. 1974.

§ 83.457 Tests of radiotelegraph auto alarm.
(a) The radio officer shall at least once every 24 when the ship is in open sea, outside of a harbor or port:

(1) Test the efficiency of the radiotelegraph auto alarm by using the testing device to determine if the apparatus will will respond to not less than 4 nor more then 12 consecutive dashes having the approximate duration of 4 seconds and the approximate spacing between dashes of 1 second, the timing to be made by reference to the seconds hand of the radiotelegraph station clock.

Noll, Edward M. “SHIPBOARD RADIOTELEGRAPH STATIONS AND OPERATOR LICENSING / AUTOALARM RECEIVER.” Marine Radiotelegraph Operator License Handbook, 1st ed., IBSN *0-672-21109-2* Chapter 1, p. 27., published by H.W. Sams, Indianapolis, IN, copyright 1975.

The identical wording is found in my October 1, 1987 Code of Federal Regulations, Chapter 47, Part 80 as:

§ 80.817 after Federal Communications Commission reorganized § 83 into a unified § 80 which was to have all the maritime regulations except for equipment specifications which were contained elsewhere in the FCC regulations, a copy of which I do not own, and the autoalarm specifications no longer are in that part as accessed by Internet.

However "Electronic Communication" by Robert L. Shrader, 6th Edition, Chapter 29-9 states that:

The radiotelegraph AA signal is 1 minute of alternate 4s on and 1s off A2A radio transmissions on 500 kHz.

The AA receiver times received dashes, accepting only those between 3.5 and 6 s long, if separated by 0.1 to 1.5 s spaces. After three such received dashes are accepted into memory the receiver relay closes, ringing bells and lighting lights in the radio station, on the bridge, and in the radio operator’s quarters.

Shrader, Robert L., “Chapter 26-9 MARITIME RADIO, Auto Alarms and Silent Periods.” In _Electronic Communication_, 6th ed., pp. 594–95, published by Glencoe, Macmillan-McGraw-Hill, Lake Forest, IL copyright 1991.

73
David J. Ring, Jr., N1EA
ex R/O USMM


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## trotterdotpom (Apr 29, 2005)

Baulkham Hills said:


> As noted four 4 second dashes would activate the A/A but the autokey would actually send twelve 4 second dashes with one second spacing followed by SOS (3 times ) followed by de and callsign (3 times). Then the actual distress message.If the AKD was not manually stopped it would go on for 36 hours of course without the distress message. A coast station could send it as well or another ship close by......"


On later models, following the Distress Signal (SOS X3 de Callsign X3), the Autokey would send two 12 second dashes which were supposed to be for direction finding purposes.

John T


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## Varley (Oct 1, 2006)

I am with the 4 dash brigade. I sailed with both the Seaguard and Lifeguard (on which I did my ticket).


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## spaarks (May 1, 2009)

I think the autokeyer sent 4 dashes, any 3 of which would activate the autoalarm. The 1960's Marconi autoalarm was an electromechanical wonder, whereas the AEI one, the Q29, was all valves and relays. The sequence had to be learnt off for the PMG exam. "S1 closes, energising SA....." and so on! 
The system worked great especially in winter in the Med, when you'd frequently get woken up at night by distresses in the North Sea - quite unnecessarily re-broadcast by PCH, the very powerful Dutch station.


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## Baulkham Hills (Jul 11, 2008)

There is a good write up on this site about Marconi Marine equipment. Probably a member of SN





Marconi Equipment


Colin G4GBP Amateur Radio Enthusiast



alt.g4gbp.co.uk


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## sparks69 (Dec 18, 2005)

Did they ever invent an Auto Alarm that could hear the signal through night time static in the tropics ?
When I was visiting RAF Gan, they had an AA which if I remember correctly was just one continuous carcophy of static at night.


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## searover (Sep 8, 2007)

Ron Stringer said:


> Sailed with the Type-M (_Vigilant_) auto alarm on several ships. It always managed to raise eyebrows on fellow crew members if they saw me setting it to work when I was going off watch. The vibrating reed had to be set in motion by means of giving a sharp blow to the side of the cabinet, while at the same time it was necessary to depress and spin the spring-loaded knob on the front panel (so as to engage its spindle with a gear on the motor shaft).....


I'm sorry you had to remind me of the "vibrating reed". On the good ship ss Appledore, in 1955, the alarm bell was just above my bed. The contact on the "reed" was burnt. I was rudely awakened on multiple occasions because the A-Alarm had been triggered. Invariably a false alarm. This was my first ship as sole R/O so I dutifully tried to keep the equipment going by burnishing the contacts to a bright sheen but, lo and behold, that only lasted a couple of days before I was struggling to do what was right, again. In the middle of the Pacific en route to Nahkodka near Valdivostok or wherever. Many moons away from a reed replacement. Can't remember what the final resolution was - but I longed to an undisturbed sleep and another ship.


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## gwzm (Nov 7, 2005)

As I mentioned above, my recollection from the PMG course and sailing with Marconi and other AAs in the early 60s, it was three dashes to set the bells ringing. The Marconi book Wireless At Sea The First Fifty Years mentions the development of and compulsory fitment of AAs from 1927 on but is silent on how many dashes were needed to set the device off.
in One Hundred Years of Maritime Radio by W D Goodwin he says: “the special receiver responded to three, four-second dashes spaced one second apart. After considerable testing the device was finally approved by the British Board of Trade in 1927.”
So, it looks like the question is not how many dashes but when did the regulations change?
It was all a long time ago for me and it doesn’t matter now in this modern GMDSS world.
Happy days
gwzm


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## P.Arnold (Apr 11, 2013)

Ron Stringer said:


> Back in the 1950s a common PMG question required you to draw an auto alarm and describe how it registered an Alarm signal and actuated the alerting bells. Hatches, pawls and cams featured strongly.


At Riversdale we had an AEI AL90. (I think). In the orals, I was asked what relay did what on one of the dashes. I hadn’ t a clue. 
When resitting the orals, I had learn’t everything about the AA.
The same examiner referred to his ‘case notes’. Said to me. “I think you will fully know the workings of the AL90 now”.
Then went on to ask me a question about another piece of gear!!


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## Nigel Fisher (Sep 22, 2010)

Baulkham Hills said:


> As noted four 4 second dashes would activate the A/A but the autokey would actually send twelve 4 second dashes with one second spacing followed by SOS (3 times ) followed by de and callsign (3 times). Then the actual distress message.If the AKD was not manually stopped it would go on for 36 hours of course without the distress message. A coast station could send it as well or another ship close by. Sometimes the A/A would go into alarm especially at night and it would be a coast station in Canada and you would be rounding the Cape.I think generally coast stations would take over the distress and co-ordinate the rescue. Silence periods would still be observed but the station involved would still send the twelve 4 second dashes and an updated distress message proceeded by SOS.Every message pertaining to the distress was proceeded by SOS and the recommended speed was 12 words per minute. I still practically fall out of my chair when i hear an SOS sent in some old movie, a bit like Pavlov's dog I suppose. Normal working was supposed to move to 512 kc/s but this was in theory because ships out of range of distress reception would go merrily calling until the QRT distress was sent in a very stern manner.
> On occasion in a dead part of the world radio wise some one would check that the AKD was actually keying the emergency transmitter and not stop it until well past the 4th dash then realized that they were actually starting a distress call then it would abruptly stop followed by total silence, For all it's faults it was a very good system in the days before Satellite communication, I personally was not impressed with GMDSS and I generally found the person responsible for it, had very little knowledge or interest in it. When I left the radio room I never wanted anything more to do with GMDSS. On occasion when I was called to make it work it was usually operator error. Even as it was introduced I felt it was a poorly conceived concept. But that's my opinion.(to quote Mandy Rice Davis "he would say that")
> While not a big fan of Marconi Marine equipment (especially their radars) I must pay complement to their a/a and akd being robust and reliable.


Yep, the correct auto alarm transmission was 12 four second dashes each separated by a one second space. However, A/A receiving equipment would actuate after receiving any four correct dashes and spaces. Back in the late 1970's I purchased a Marconi Seaguard auto alarm which is now residing in our garage. Information with the unit indicated that it had ben originally installed during the fitting our of the Commonwealth (of Australia) Lighthouse ship Cape Don/VLFQ. The Cape Don Society was contacted to see if they wanted it, but difficulties arose due to the ship is in Sydney and I live in Western Australia. Add in Covid-19 and so the A/A still resides in my garage.


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## Baulkham Hills (Jul 11, 2008)

Twelve 4 seconds and 1 second spacing I was referring to the akd. Of course the auto alarm worked on any four consecutive 4 second dashes and one second spacing should operate the auto alarm.
Another point is that the auto alarm would not reject a dashes and spaces that was not exactly correct, in case the operator on the vessel in distress was sending it by hand. In fact the radio room clock is segmented to facilitate this.
It is amazing that a Seaguard is in garage in Western Australia.


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## Varley (Oct 1, 2006)

It would not be in my garage but whirring away in by lounge for all to appreciate. A clickety clickety clack AKD would be an ideal pairing.


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## R651400 (Jun 18, 2005)

Interesting comments using the AKD to test the Auto Alarm before going off watch.
Was keying the AA test oscillator with the AKD an eventual station requirement?


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## Dimples82 (Aug 24, 2014)

For the full info regarding the signal suggest you have look at the HMSO Hanbook for Radio Operators, this gives full detail regarding the signal, operations over 1 min & the A/A operating after 4 x 4 sec .dashes, with a spacing of 1 sec. between each dash (in case you have to send it by hand) and also that provided by AKD units should be capable of.
For Circuit if information, Daniallson & Mayo's "Marine Radio Manual" has a step buy step guide on the circuit of the all valve Lifeguard (it may also have the old camshaft version - sorry memory is not so good.


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## sparks69 (Dec 18, 2005)

A B E H D C S 
I won't regale you with the (rude) mnemonic I made up to remember them for my exam in 1965


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## Dimples82 (Aug 24, 2014)

It was also in my Part 2, however, after trying time and time again to understand how this infernal AA worked, would believe me if I admitted it clicked on the evening prior to exam day, and low and behold, there was a question on it in the exam paper, and I actually picked to answer it, and I passed !


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## Batley Bill (Feb 11, 2012)

I sailed in the late 60s early 70s. I sailed mainly with Seaguards and Lifeguards, but I seem to remember sailing with an older piece of kit that only needed three dashes. I think it was a Marconi Vigilant.


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## gordonarfur (May 27, 2018)

I still have my PMG note book from the late fifties which contains a circuit diagram and my written notes on the workings of the selector mechanism of the AA. They state quite clearly that the alarm will be activated and the bells ring on receiving three four second dashes subject to them adhering to the constraints imposed by the makers. i.e. the period between each dash and of course the length of the dash. The PMG exam that year required one to draw and explain the operation of the mechanism. Yippee I passed the exam and promptly put away my notes for the next 61 years.


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## pippin (May 13, 2008)

Ah - the Seaguard.

Something nobody else has mentioned:

The scuffed knuckles when spinning the knurled knob to get the wretched motor to turn.

The knob had to be pushed in to engage the mechanism and spun at the same time.

Why, oh, why, did they locate it so close to the chrome-plated escutcheon surround that one's knuckles would catch on the edge of it?

Happy memories of 55 years ago!!

Incidentally, distress communications were not specified to be sent at 12wpm. 
My PMG handbooks dating from the 20's all state:

"The speed of transmission in cases of distress, urgency and safety shall not in general exceed sixteen words per minute."


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## spaarks (May 1, 2009)

spaarks said:


> I think the autokeyer sent 4 dashes, any 3 of which would activate the autoalarm. The 1960's Marconi autoalarm was an electromechanical wonder, whereas the AEI one, the Q29, was all valves and relays. The sequence had to be learnt off for the PMG exam. "S1 closes, energising SA....." and so on!
> The system worked great especially in winter in the Med, when you'd frequently get woken up at night by distresses in the North Sea - quite unnecessarily re-broadcast by PCH, the very powerful Dutch station.


Yes, I stand corrected, it sent 12 dashes, a consecutive 4 of which would activate the alarm.


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## Nigel Fisher (Sep 22, 2010)

Baulkham Hills said:


> Twelve 4 seconds and 1 second spacing I was referring to the akd. Of course the auto alarm worked on any four consecutive 4 second dashes and one second spacing should operate the auto alarm.
> Another point is that the auto alarm would not reject a dashes and spaces that was not exactly correct, in case the operator on the vessel in distress was sending it by hand. In fact the radio room clock is segmented to facilitate this.
> It is amazing that a Seaguard is in garage in Western Australia.


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## Nigel Fisher (Sep 22, 2010)

Pics of Seaguard residing in my garage


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## pippin (May 13, 2008)

From those pics you can clearly see how the starting knob was ideally placed to cause skinned knuckles!


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## Varley (Oct 1, 2006)

I think that must be the luck of the draw. No one aimed to recruit R/Os with clumsy knuckles.


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## Ron Stringer (Mar 15, 2005)

Don't recollect ever skinning my knuckles when starting the A/A. I used the fingertips of my thumb and middle finger to spin the knob on the front panel; my knuckles were never in contact with the knob or the panel. Am I missing something (other than the scarring)?


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## R651400 (Jun 18, 2005)

Just back from a spot of holiday and checked an old text-book that it is verbatim from the GTZM manual...
The Type M Vigilant AA bell circuit is latched on the third dash. 
Why I thought it was four may have come from later model free-lance AA's.
Begs the question. 
Was it also the same for Seaguard which I never laid eyes or knuckles on?


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## IMRCSparks (Oct 1, 2007)

It always seem to have been four dashes with the 'digital' auto alarms as per the attached image of a Lifeguard 3.

You can see the four LEDs that would light up when dashes were received and the line down to the Alarm lamp from the fourth LED.

Always a source of great fun in high static areas when you could watch the led's light up consecutively and then (hopefully) reset before reaching number four. (Amazing what counts as fun when you're on a 45 day trip from Brazil to Japan rolling like a b*tch with a cargo of iron ore!)

Same with the Redifon and IMR versions as I recall.


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## Troppo (Feb 18, 2010)

IMRCSparks said:


> It always seem to have been four dashes with the 'digital' auto alarms as per the attached image of a Lifeguard N.
> 
> You can see the four LEDs that would light up when dashes were received and the line down to the Alarm lamp from the fourth LED.
> 
> ...


The Lifeguard 3 was a step backwards from the Lifeguard N - the N had a BFO, so you could use it as a 500 watch rx...


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## gwzm (Nov 7, 2005)

R651400 said:


> Just back from a spot of holiday and checked an old text-book that it is verbatim from the GTZM manual...
> The Type M Vigilant AA bell circuit is latched on the third dash.
> Why I thought it was four may have come from later model free-lance AA's.
> Begs the question.
> Was it also the same for Seaguard which I never laid eyes or knuckles on?


That was certainly my recollection from studying for the PMG in the early 60s and having to be able to draw the selector circuit for the exams. In my mind, there would have to have been a change to the type approval regulations to make activation dependent on four correctly timed dashes rather than three. However, I haven’t been able to find out when the change took place - does anyone know? It’s clear from some of the replies and photos that later AAs did indeed need four dashes to trigger the alarm. Perhaps a need to reduce false alarms triggered by static?
Happy days,
gwzm


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## gwzm (Nov 7, 2005)

Just found this drawing by Roger Bentley of the Marconi AA selector in a previous thread on SN. Shows the three relays that were latched by the selector pawls.
Happy days,
gwzm


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## pippin (May 13, 2008)

Perhaps I can clear up the confusion a bit.

The Marconi Marine VIGILANT aka TYPE M manual is dated 1953.
The selector description has a table which indicates that after three correct dashes with two correct spaces between them the actuator is poised. 
But if another dash arrives after an incorrect too short a space it will reset.
However if the third space reaches 1.6 secs the bells will ring.

I think the SEAGUARD was a horizontal version of the VIGILANT.

So - THREE DASHES!

The Marconi Marine LIFEGUARD manual of 1965 states:
"The alarm signal is actuated after registration of three consecutive correctly timed dashes and spaces, followed by a fourth dash of 3.5 sec or greater duration" (my underlining)
The meter on the front panel also indicates the number of 4-second dashes registered: 1st, 2nd, 3rd, 4th.

It complies with TSC.71 of the Ministry of Transport, reflecting SOLAS London 1960.

Mechanically and electrically interchangeable with the SEAGUARD 2.

So - FOUR DASHES

The Redifon AA1 manual of 1973 states that the selector can be internally preset to respond to three or four dashes.

So - THREE or FOUR DASHES

There you have it!!

Another related change was to the AKD sequence.

The Marconi Marine AUTOKEY manual dated 1953 states that after the distress signal it sends a 30 second long dash for DF purposes.
An addendum dated 1963 revised that to two long dashes of 11.5 seconds separated by a space of 1 second for DF purposes.

So, there you have it - again!!

E&OE!


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## gwzm (Nov 7, 2005)

Pippin,

Many thanks for your clarifications. 
gwzm


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## Ron Stringer (Mar 15, 2005)

The Type M, Vigilant and Seaguard auto alarm equipment had different receivers but shared the same selector mechanisms, with only minor changes. In the Type M Vigilant the synchronous motor was controlled by pulses derived via contacts on a vibrating metal reed. On the Seaguard the motor was controlled by pulses from an electronic oscillator.


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## pippin (May 13, 2008)

Quite right Ron.

I have just found the SEAGUARD manual, dated 1958.

The selector mechanism must differ to that in the VIGILANT of 1953.

It requires FOUR DASHES.

From all this I hope we can deduce that the change from 3 to 4 dashes occurred by about 1956.

So, there you have it - again and again and again!!!!!!

Incidentally Ron, that short-lived Marconi Marine flag in your avatar - I actually have one! Rather tattered.


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## Ron Stringer (Mar 15, 2005)

It's a long time ago now (1969?) but from my experiences with the type approval testing of the Lifeguard N the thing that I found most interesting/impressive was the calculation and implementation of the receiver's complex AGC characteristics. Had to take out simultaneous tropical QRN and powerful QRM from nearby stations to allow the selector opportunity to detect not just the 4-second dashes but the briefest of spaces between dashes.
The type approval involved continuous monitoring of the equipment lasting one month whilst installed at a Post Office site at At Margaret's Bay, in the Dover Strait. No shortage of strong QRM there!


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## sparks69 (Dec 18, 2005)

In a heavy sea the Vigilant vibrating reed thingy could stop vibrating when the vibrations synchronized with the shuddering of the ship as it went up one side of a big wave. I sat, strapped in my radio room chair, and actually saw & heard this happen !! The mate on the 4 to 8 went bonkers with the bl++dy great bell clanging on the bridge.
Unbelievable !
We had a huge box of the vibrators in cans with valve bases in the spares cupboard. I think the regs went over the top when they specified how many spares one had to carry. [No unsavory comments required please.]


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## R651400 (Jun 18, 2005)

Tried to make a semi-automatic key from one of those valve based vibrators for the dot side but couldn't get the beggar to go slow enough.
Hope you don't mind me clarify but this vibrator pack was for the GTZM receiver PSU's and nothing to do with the Vigilant Type M vibrating reed selector motor drive..
I must've been lucky in GTZB as I never had any trouble with the Vigilant except one with a case badly pitted from rust as it was close to the radio room port-hole !!


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