# Auto Alarms Responding to SOS ... (?)



## Worldspan (Jan 2, 2012)

Back in the 1950s, someone once told me that there were auto alarms which were activated by the signal SOS. Is this true or were the only alarms those which we all knew ... and the circuit diagrams of which we had to learn by heart?

W


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## Tony Selman (Mar 8, 2006)

To the very best of my knowledge there were no auto alarms that could respond to the letters SOS. They had to be triggered by the 4 second dashes with one second intervals or as we all experienced 4 second bursts of QRN with one second intervals.


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## CrazySparks (Apr 21, 2008)

I'm with Tony Selman on this one - never heard of such a device - not from old time college lecturers or old R/O's at sea. Just imagine what QRN could do with those one second dots! Offhand 
On a technical level, I'd say that the probability of ...---... appearing out of noise is very high. With either carrier detection or modulation detection, the time required to detect a dit would certainly be too long to differentiate a genuine signal from noise, so the '...' is a non-starter. The _ _ _ will also pop up very frequently. I think the false alarms would have driven an RO insane!
Modern digital radio systems use opening signal sequences that have very low probabilities of arising in noise, and which are mathematically very well defined. They have a property termed 'low cross-correlation' with noise - which means they don't readily appear in noise, and also good 'auto correlation' which means that if you compare the receiver output with a copy of the signal you want, you can have a defined confidence in correctly detecting the signal. This is quite a complicated field and I won't harp on here. Look up Barker Codes for further insights.


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## rusty1946 (Aug 15, 2008)

As far as I know Marconi Marine made autoalarms in the 1950's dont know what triggered them whether it was the dashes of the opening sequencies or not


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## trotterdotpom (Apr 29, 2005)

The Seaguard, a boxful of cams and pawls, responded to the 4 second dashes, the same as the later electronic auto alarms. 

John T


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## mikeg (Aug 24, 2006)

Tony Selman said:


> To the very best of my knowledge there were no auto alarms that could respond to the letters SOS. They had to be triggered by the 4 second dashes with one second intervals or as we all experienced 4 second bursts of QRN with one second intervals.


Makes me wonder how they initially determined the number of dashes to trigger the alarm. I'd have thought an additional dash would have markedly decreased false alarms due to QRN


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## Ron Stringer (Mar 15, 2005)

mikeg said:


> Makes me wonder how they initially determined the number of dashes to trigger the alarm. I'd have thought an additional dash would have markedly decreased false alarms due to QRN


You are right, Mike, but increasing the number of required dashes would have increased the possibility of interference causing the resetting of the count and therefore the likelihood of missing a genuine alert. The whole thing was a mass of compromises and the design of the testing equipment was far more difficult and demanding than the design of the auto alarm itself. You not only had to design the dash generator, you had to be able to vary and set the max/min timings for dashes and spaces and to be able to generate and introduce various levels and types of interference. A nightmare at type-approval testing time, since all this had to be done with the equipment being cycled through the various climatic and environmental conditions.

When all that was over, the equipment was then taken down to St. Margaret's bay, installed in the terminal building for the cross-Channel telephone cable and connected to an antenna. There it was connected to a tape recorder with a loop facility that was able to record 2 (IIRC) minutes of the receiver audio output, 1 minute either side of the alarm being activated. It was left there for one month and the activations were logged. After each alert was received/activated, the equipment was reset and put back on watch and the audio loop was transferred to a reel-to-reel tape. The overall results obtained were later compared with the 500 kHz log of GNF.

During the on-air testing, I used to drive down once a week to meet Willie Horwood or John Proctor of the PMG T/A department and review progress of the "Lifeguard N" (and some years later the "Lifeguard II"). The comparison count was always in favour of the A/A equipment - it recorded many genuine alerts that GNF did not. None of them were in the Channel I hasten to add, they ones that GNF missed were all in the Baltic or Western Mediterranean.

Still it was reassuring that we never missed any genuine alerts. Better that than sacrificing alerts for the sole purpose of cutting back on false alerts from static. It was a nuisance to be roused from slumber in the tropics by a false alert, but nobody died as a consequence.


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## sparks69 (Dec 18, 2005)

They had an Auto Alarm on all the time at the RAF Station (callsign MEX) on Gan Island.
Not sure what use it would have been considering the QRN would almost be QRN5 all night. My memories were that they were next to useless once the static crashes & bangs got going.


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## Ron Stringer (Mar 15, 2005)

R651400 said:


> I don't get the reasoning behind this comparison. All British coast stations had a finite area of distress responsibility and apart from maintaining the usual silence on 500 kc/s it's highly unlikely that GNF would be interested in any distress in the areas mentioned. I would however expect a ship's auto alarm to activate at such distances and even further.


The GPO recognised the difficulty of producing a laboratory test regime that could be confidently claimed to completely simulate the conditions existing on 500 kHz in all areas of the world. Although they appreciated the safety-critical nature of the A/A, the GPO's technical management were unwilling to have their test engineers spend weeks sailing around the tropics or other difficult receiving areas, in an effort to prove that such equipment would operate reliably in service. So, having subjected the equipment to all the laboratory tests that they had developed over the previous 30 or 40 years, they applied a belt-and-braces approach by putting the equipment under supervision in as near similar conditions as they could. That is, in a permanently-manned station close to the sea (about 20 metres from the high-water line) and in a 500 kHz high traffic zone (Dover Straits). There, over a period of 4 weeks, its performance in receiving alarm signals on 500 kHz was checked (as a performance control) against the 500 kHz logs at the nearest coast station some 40 km to the North of the test station at St Margaret's Bay (at the foot of the cliffs near Dover).

Radio regulations required the recording in the Radio Logbook of all ship radiotelegraph stations, the salient details (time, frequency etc.) of all alarm and distress signals received. There was no mention of recording only nearby signals. Having spent some years at sea, I had expected that the same obligation would apply to coast station radio operators and was surprised that the A/A, with its virtually sea-level location under the cliffs, using only a simple antenna and a TRF receiver, was able to detect, record and activate alarms from transmissions that were not recorded at the coast station. The latter had much more sophisticated receivers and more extensive antenna systems.

Maybe I ought not to have been so surprised, given the identity of the station chosen as the control. 

ps The GPO test engineers were not at all surprised and were highly amused at my naïveté.


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## trotterdotpom (Apr 29, 2005)

Ooooooh! Anyone here who owns up to working at GNF? Over.

John T


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## Troppo (Feb 18, 2010)

The Lifeguard N made a great watchkeeping receiver, especially with the BFO.


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## Naytikos (Oct 20, 2008)

I once had an SAIT auto-alarm (which I'm sure Ron will tell us was really made by someone else) which false-triggered several times a day static or not. It took a month before I found the cause to be a leaky coupling capacitor at the aerial input.


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## Graham P Powell (Jun 2, 2007)

Being a heavy sleeper, I had the 2nd mate come down from the bridge one night to wake me up as the auto alarm bell was ringing just above my head and
I hadn't heard it.....
I found whenever it went off that the distress or whatever was hundreds of miles away.
rgds
Graham Powell


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## trotterdotpom (Apr 29, 2005)

Naytikos said:


> I once had an SAIT auto-alarm (which I'm sure Ron will tell us was really made by someone else) which false-triggered several times a day static or not. It took a month before I found the cause to be a leaky coupling capacitor at the aerial input.


Water in the auto alarm will do that.

John T


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## mikeg (Aug 24, 2006)

I recall it was the 13th of the month when the AA went off at night due QRN, approx 02:00 & again 04:30 local got back to cabin for Zzz at approx 04:45 followed by ring from the bridge - fault on radar. All part of seagoing life


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## holland25 (Nov 21, 2007)

Possibly one of the upsides of being a Blue Funnel 2R/O. The 1st R/O's cabin was next to the Radio Room, mine was on the main deck outside the saloon. I never had a broken night because of false AA triggers.


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## Naytikos (Oct 20, 2008)

John T:
(LOL)(LOL)(LOL)


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## alex page (Mar 15, 2006)

The Marconi Vigilant required a 3 dash sequence to trigger it. The simple TRF receiver worked amazingly well, static was a problem but minor considering its basic design. I have often received northsea alarm signals in the central med.One thing I could never understand was having to learn and draw all the circuits and cam operation for your ticket, when you had a manual.Teaching the use of the manuals would have been more productive.

Rgds A


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## charles henry (May 18, 2008)

Live and learn
I always thought they were designed to respond only to static crashes.....
Chas


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## sparks69 (Dec 18, 2005)

A B E H D C S - the names of the relays in (I think) the MIMCO Seaguard autoalarm I can't repeat the mnomemic which I made up to memorise the workings of the thing it would be censored !


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## Klaatu83 (Jan 22, 2009)

The Auto Alarm was one of the things that came out of the titanic disaster. It did not respond to "S-O-S", but, as Tony Selman wrote, to a specific series of 4-second dashes and one-second intervals, transmitted (I believe) on 500 khz. The actual alarm was required to sound in the radio shack, the Radio Officer's stateroom, and on the bridge. The idea was that, in the event that it went off when the Radio Officer was off duty, or asleep, then he would be able to hear it in his stateroom; and even if he was absent from his stateroom (at mealtimes, for example), then the Bridge watch would hear it, and be able to contact him. The Auto Alarm was finally abolished in February 1999, when the new GMDSS communications came into effect, and many ships ceased to carry Radio Officers at all anymore.


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## Varley (Oct 1, 2006)

Klaatu83 said:


> The Auto Alarm was one of the things that came out of the titanic disaster. It did not respond to "S-O-S", but, ...
> 
> I am sure that automation was being dreamed up but the Merchant Shiiping (Wrieless Telegraphy) Rules 1920, "ships of class II .... are required to carry, in addition to a certificated operator, one watcher if the voyage exceeds eight hours but does not exceed 48 hours from port to port and two watchers if the voyage exceeds 48 hours from port to port".
> 
> ...


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## trotterdotpom (Apr 29, 2005)

Varley, I found a website called "The Telegraph Office" which says the Urgency Signal XXX (and the Safety Signal TTT) was in use at the same time as CQD, so it must have started in the early 1900s at least.

Just occurred to me that sending an Urgency message by Aldis lamp could be the origin of the expression "A flash in the PAN".

John T


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## Ron Stringer (Mar 15, 2005)

Varley said:


> As usual, once two extra wages (or bonuses anyway) were added to the opcosts there would have been pressure to find some automatic alternative.


Nothing changed - hence the GMDSS some 70 years later. [=P]


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## hughesy (Dec 18, 2007)

did'nt you have to log an A/A test before going off watch??

all the best
Hughesy


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## Troppo (Feb 18, 2010)

....and coming on watch....


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## Troppo (Feb 18, 2010)

Klaatu83 said:


> The Auto Alarm was one of the things that came out of the titanic disaster. It did not respond to "S-O-S", but, as Tony Selman wrote, to a specific series of 4-second dashes and one-second intervals, transmitted (I believe) on 500 khz. The actual alarm was required to sound in the radio shack, the Radio Officer's stateroom, and on the bridge. The idea was that, in the event that it went off when the Radio Officer was off duty, or asleep, then he would be able to hear it in his stateroom; and even if he was absent from his stateroom (at mealtimes, for example), then the Bridge watch would hear it, and be able to contact him. The Auto Alarm was finally abolished in February 1999, when the new GMDSS communications came into effect, and many ships ceased to carry Radio Officers at all anymore.



Wow!

You learn something new here everyday.

Fancy that.


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## trotterdotpom (Apr 29, 2005)

I don't recall testing the Auto Alarm when I went on watch, but I always was a lazy git. Why would you do that anyway? If the gear was faulty, you'd soon be aware of a distress when you started listening to 500 kcs and be able to go "Whoops". The fault would show up when you tested the AA when you went off watch.

John T


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## Troppo (Feb 18, 2010)

The rules, mate....always test the aa on and off watch.

Log book entry to that effect....


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## sparkie2182 (May 12, 2007)

Yep.........

Sack Trotterdot.


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## Ron Stringer (Mar 15, 2005)

sparkie2182 said:


> Sack Trotterdot.


Hang on, better check the battery SGs before you let him ashore!


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## trotterdotpom (Apr 29, 2005)

OK ..."AA tested and off" does sound familiar now that I think of it, but what's an SG?

John T


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## Pat bourke (Jun 30, 2007)

trotterdotpom said:


> OK ..."AA tested and off" does sound familiar now that I think of it, but what's an SG?
> 
> John T


Specific Gravity !!

Pat


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## sparkie2182 (May 12, 2007)

Jeeeeeeeeeeeeeeeeeeez..............


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## Bill Greig (Jul 4, 2006)

And don't forget to test the lifeboat transmitter at least once a week. Where is it kept anyway?!!
Bill


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## trotterdotpom (Apr 29, 2005)

It's under the desk with your feet on it. I always found it was easier to put the lid back if you cut the lead and chucked the headphones away.

John T


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## Bob Murdoch (Dec 11, 2004)

But DO NOT test its flotation ability.
Cheers Bob


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## Troppo (Feb 18, 2010)

trotterdotpom said:


> It's under the desk with your feet on it. I always found it was easier to put the lid back if you cut the lead and chucked the headphones away.
> 
> John T




Ha ha ha!

Spot on!


(Thumb)


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## Varley (Oct 1, 2006)

I rigged Tilapa's liefboat set in sight of Niton's aerials and still didn't raise a reply (Salvetta? Dustbin shaped, cetainly too big to go under the desk).

Astonished poor Filipino R/O on Alvand when sent him off in the lifeboat crew to test it for real (using reserves Tx with dummy load still 'blew his head off'). 

They were, nonetheless, essential - they served to maintain the upper body circulation, distracting the mind from an imminent demise. One instruction book was llustrated with the operator in the sea attached by webbing - I can only assume this was an attempt to provide some humerous reading for the occupants as well.


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## trotterdotpom (Apr 29, 2005)

Varley: "I rigged Tilapa's liefboat set in sight of Niton's aerials and still didn't raise a reply..."

Niton must have been as bad as North Foreland (mentioned on another thread) ... allegedly.

Roger Cliff, RO on the Gothic when she had the fire, used the Lifeboat Transmitter for all communications until the ship was back in port. He got a big write up in the Marconi Mariner about it.

John T


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## Varley (Oct 1, 2006)

John,

Like the Gothic story. I wonder if the main aerial was used (and if so how he got the LB set to tune and couple into it).

Should I remember the Mariner or was this shore staff only?

David V


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## Ron Stringer (Mar 15, 2005)

The "Mariner" was produced bi-monthly and was sold at all depots to whomsoever was willing to buy it. When I was at sea in the 1960s, it was priced at 6d. and was always purchased as much for the list of postings (which R/Os were on which ships) as for the articles that it contained. As those lists only came out every two months and were based on returns for the month prior to printing, they were always a few months out of date but that was of no concern in those days.

As time on articles fell and two-year trips became very rare and the norm fell to maximum 3-month trips, the lists became pretty useless other than to show where someone had been, rather than where he currently was serving.


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## Moulder (Aug 19, 2006)

Click here for a link to a gallery photo of the front cover of one of the editions of the Mariner.

Steve.

(Thumb)


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## Troppo (Feb 18, 2010)

Are the mags on line somewhere?

Would love to read them.


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## andysk (Jun 16, 2005)

trotterdotpom said:


> Varley: "I rigged Tilapa's liefboat set in sight of Niton's aerials and still didn't raise a reply..."
> 
> Niton must have been as bad as North Foreland (mentioned on another thread) ... allegedly.


Used to test the portable on Edinburgh Castle in East London, within sight of ZSA, who would come out on to the balcony of the radio station and wave to us that he had heard us OK.


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## trotterdotpom (Apr 29, 2005)

Varley said:


> John,
> 
> Like the Gothic story. I wonder if the main aerial was used (and if so how he got the LB set to tune and couple into it).
> 
> ...


I think he used the equipment's wire aerial as everything on the ship was pretty knackered, but I could be wrong. It was a pretty intrepid tale but I mainly remember it because I knew Roger at Bridlington NESWT. I've always hoped he would show up on SN sometime.

I don't remember ever paying for The Mariner, I think it just showed up on the ships. It often contained some interesting articles and photos.

John T


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## david.hopcroft (Jun 29, 2005)

I rigged the aerial out on the bridge wing and was surprised to find later on comparing noon QTH's that it was nearly 100 miles. I was well pleased and the Capt was impressed. The two stewards whose station was to crank it were NOT pleased !!

David
+
It was one of these, whose name I can't remember.


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## sparkie2182 (May 12, 2007)

"I don't remember ever paying for The Mariner...............

Or the beer, or the Bar-b-Q, or the taxi........etc...etc.....


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## Ron Stringer (Mar 15, 2005)

sparkie2182 said:


> "I don't remember ever paying for The Mariner...............
> 
> Or the beer, or the Bar-b-Q, or the taxi........etc...etc.....


Are you really sure you're not from Yorkshire? [=D]


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## Bob Murdoch (Dec 11, 2004)

The Mariner was free so far as I remember.
Even when on the Canadian coast it was sent out to me. Wish I had kept them all now.
Bob


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## Naytikos (Oct 20, 2008)

Posted by Trotterdotpom


> _It's under the desk with your feet on it. I always found it was easier to put the lid back if you cut the lead and chucked the headphones away_.


That was supposed to be the tradition, but I never sailed on a ship where there was room. Even the neat scandinavian one supplied by SAIT couldn't go under one of their consoles.

Anyway around 1979 a DNV surveyor got all upset because the lifeboat radio wasn't kept on the bridge. When asked the logic of the R/O having to go upstairs to collect it and then down four decks to the lifeboats he had no answer, only "that's the rules". So I put it on the chart table until he went ashore and then returned it to the radio room. And went through the same dance the following year and so on until leaving the ship.
This is the same surveyor who said it was not allowed to have a CO2 fire extinguisher in the radio room because it was 'occupied space'. BUT it is required for the radio room fire extinguisher to be CO2; powder or foam are not acceptable. 

Catch22!


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## Baulkham Hills (Jul 11, 2008)

Hi


The Mariner magazine were a well produced company magazine, never remember paying for it, it was posted home and I really liked the cartoons which appeared in it on a regular basis. I can't remember who drew them but they were of a very high standard.

Cheers


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## Graham P Powell (Jun 2, 2007)

Some of the cartoons in the Mariner were drawn by GKA R/O Joe Mccabe.
Some of us are lucky enough to have some of the ones about GKA he did. 
They would be meaningless to most people but hilarious to us!.
Joe is still around. He's in his 70's and looks much the same as when I first
met him.
rgds
Graham Powell


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## Ron Stringer (Mar 15, 2005)

Baulkham Hills said:


> Hi
> 
> 
> The Mariner magazine were a well produced company magazine, never remember paying for it, it was posted home and I really liked the cartoons which appeared in it on a regular basis. I can't remember who drew them but they were of a very high standard.
> ...


It won awards several times for the best House magazine in the UK. Originally (in my day) produced by H R (Roy) Whitticase and then, following his retirement on grounds of ill-health, it became the province of Rosemary Gibson who took it on to win several more prizes.


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## stocksie (Apr 22, 2008)

1950 to 1970 Mariner cartoonist was Norman Mansbridge who was a serving R/O.. Out of East Ham. He went on to contribute to several Newspapers.


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## Roger Bentley (Nov 15, 2005)

Recently was cleaning up items in the loft and came across this strange cave drawing in one of the old note books I found. c.1949 Did we really have to draw this type of thing for the PMG exam? Cheers, Roger


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## holland25 (Nov 21, 2007)

I have been following this thread with interest and the phrase "Hotch and Dash cams",kept going through my mind and I thought I was making it up. I see however from the drawing that they did exist.


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## Ron Stringer (Mar 15, 2005)

Don't forget the pawls.


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