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256:, or under the heel of your boot. There is no need to crush the end of the tube completely flat. All that is required is to crush and dent the tube sufficiently to break the glass vial, thereby releasing the liquid contained within. Check the inspection hole next to the brass safety strip. If the inspection hole is unobstructed (i.e. it is possible to see right through to the other side) then the countdown has started and the brass safety strip (holding back the striker) should be removed and discarded. However, if the inspection hole is obstructed (before the safety strip is removed) the striker has been released so the pencil detonator should be discarded and another one selected. The final step is to insert the end of the pencil which has the actual
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368:. For example, a pencil detonator designed to fire 24 hours after being activated could in reality give a 30-hour delay - if the weather was very cold. Similarly, during hot weather pencil detonators designed to fire after a 12-hour delay could in reality trigger detonation within 10 hours. The main virtue of pencil detonators is their small size and light weight, plus the fact that they are very quick and easy to use. These are important points during covert operations.
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under tension and held in place by a thin metal wire. The timer was started by crushing the copper section of the tube to break the vial of cupric chloride, which then began to slowly erode the wire holding back the striker. When the wire eventually parted, the striker was propelled down the hollow
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For very high-value targets it is recommended that two pencil detonators from different batches be used together. That way if one detonator fails the other will almost surely blow the charge. Note that if both detonators were going to work, the explosion will occur at the earlier of the two times;
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Another type of time pencil had a percussion cap but no detonator attached. Instead there was a crimping attachment at one end to allow pyrotechnic fuse to be crimped on. When a time pencil of this type fired, it would light the fuse which would burn towards a detonator crimped onto the other end.
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The delay could be set from a matter of minutes to hours. Manufacture was entirely by MD1. Generally speaking L-delays were slightly less reliable and had shorter delays, but were more reliable underwater (if a No. 10 fuze developed a leak, water would dilute the corrosive liquid and increase the
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two or three minutes in an hour's delay, and plus or minus an hour in a 12-hour delay, though environmental conditions could affect this. The switches were typically issued in packs of five, all the switches in a pack having the same delay. In use, two switches with the same delay (from different
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time delay, which can range from 10 minutes through to 24 hours. No. 10 delays were normally issued in a tin of 5, all of the same delay, while L-delays were issued in a larger tin which included a mixture of different delays to suit a variety of operations. The time delay of a No. 10 varies
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known as the "Lead Delay switch" or officially "Switch, No. 9, L Delay". Instead of relying on the chemical action of a corrosive liquid on metal (which was subject to temperature variation), it used a piece of metal under stress – the metal in question being a
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of the corrosive liquid in the vial. It is widely reported that the wire thickness varied also, but in fact all used the same diameter of wire. The time delay of a No. 9 is determined solely by the thickness of the notch in the wire, the
345:(which did not require a booster) were particularly useful during the sabotage missions in which they were often employed. There were also a number of special charges issued with a time pencil already incorporated e.g. some types of
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burns at around half a metre per minute, it is not practicable to provide delays of more than a few minutes in this way. It was also possible to connect a pencil detonator to so-called "instantaneous fuse" (not to be confused with
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Approximately 12 million pencil detonators were produced in
Britain during the war. However, in recent years they have been superseded by electronic timers which are more accurate and provide much longer delay times.
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of plus or minus 15 minutes. Both No. 9 and No. 10 delays were also significantly affected by the ambient temperature, and were issued along with a chart of temperature corrections—but no
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used a captured
British pencil detonator inserted into a block of British plastic explosives weighing approximately two pounds. The bomb was set to 30 minutes and detonated as planned, but
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could not prepare the second block, though. He got rid of it while driving through the forest to the airfield. His driver, Leutnant Erich Kretz, reported seeing
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After being activated a pencil detonator is silent in operation. It does not fizz or make any other noise. However, unlike
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Number Ten Delay Switch (official name, "Switch, No. 10, Delay" and often referred to as a "timing pencil"), was made of a
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timers, pencil detonators only give approximate time delays. For example, a 2-hour pencil detonator might be accurate to
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Arms Tech LS-1 Time Delay - a modern pencil detonator which uses same operating principle as "Switch, No. 9, L Delay"
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An array of World War 2 pencil detonators displayed at the Museum of the
British Resistance Organisation at the
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Number ten delay switches had delays ranging from 10 minutes to 24 hours and were accurate to within
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packs if possible) would be placed in the explosive charge in case one switch failed.
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5 minutes, whereas the version offering a 6-hour delay could have a
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Electronic fuze detection method (cannot detect pencil detonators)
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of 1942. The ship exploded over an hour later than anticipated.
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Pencil detonator used in the July 20 plot in 1944 exhibited in
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thus this method will also slightly reduce the average delay.
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during a part of the film detailing the July 20 plot.
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49:. Unsourced material may be challenged and removed.
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477:throw something into the woods in his mirror.
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411:Pencil detonators saw heavy use during the
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485:Time pencils figure in the 1961 war movie
269:Another, subsequent type was developed by
252:tube containing the cupric chloride with
109:Learn how and when to remove this message
190:Cutaway diagram of a No. 10 delay switch
16:Time fuze used by British Special forces
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606:Additional photographs of time pencils
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47:adding citations to reliable sources
562:. Roundwood Press. SBN 900093-22-6.
231:at the other end of the detonator.
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576:. FilmReporter. Archived from
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373:Boxes of No. 10 delay switches
265:L-Delay ("No. 9 delay switch")
145:designed to be connected to a
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421:Special Operations Executive
600:Photograph of a time pencil
560:Winston Churchill's Toyshop
243:Using a No. 10 delay switch
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127:Parham Airfield Museum
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438:during the
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366:thermometer
335:temperature
301:safety fuse
163:Aston House
151:safety fuse
139:time pencil
632:Detonators
542:References
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141:is a time
69:newspapers
531:Primacord
362:precision
354:clockwork
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558:(1971).
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318:nominal
224:striker
196:British
83:scholar
467:Hitler
429:amatol
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129:, 2007
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