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| Trip Mechanism No. 4 | Trip Mechanism No. 5 |
| This operates on the hair trigger principle. Operated by a trip wire attached to the spindle seen at the bottom of the photo. | Combination mechanism, can be used as pressure, pull or release depending on the position of the stud in the slot. |
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| Percussion Igniter Mk. 3 | Switch, No. 1, Pull Mk. I |
| Designed as a fuze lighter it was also capable of being used as a boobytrap mechanism. | The switch is fitted with the later spring snout. |
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| Switch, No. 2, Pressure Mk. I | Switch, No. 2, Pressure Mk. II |
| The base plate on this switch is attached by two brass bolts and a larger hole is drilled in the base to hold the pressure head in transit. | Note the body cast in one piece. Developed by MD1 this was the main British Pressure Switch used during the Second World War. |
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| Release Switch | Switch, No. 3, Release Mk. I |
| This is (I believe) the original release switch as first produced by MD1. When adopted by the British as the No. 3 Mk. I release switch an additional spring was added. | Developed by MD1, this was the main British release switch of WWII, likely used for a time after the war as well. |
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| Switch, No. 4, Pull Mk. I | Switch, No. 5, Pressure Mk. I |
| Developed by the SOE in about 1943 this switch was used well into the 1980's and may well still be in service. | Also developed by SOE in about 1943, this pressure switch was also used by the American OSS known as "Firing Device, Pressure, Type A3". Used into the 1980's at least, this switch may still be in service. Wartime switches were painted greeen, postwar switches were painted tan. |
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| Switch, No. 6, Release Mk. I | Switch, No. 7, Pull/Pressure Mk. I |
| Also developed by SOE in 1943 this switch was used by the OSS as the "Firing Device, Release, Type A2. This switch remained in British and Canadian service well into the 1980's and perhaps beyond. | This was an electrical switch that could be set for between 5 and 35 pounds pressure or release. |
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| Switch, No. 8, Pressure Mk. I | Switch, No. 9, "L" Delay, Mk. I |
| Also known as the "Pistol, Ground spike" this
device was originally designed to take a normal .303 rifle
cartridge. later a special bullet (see photo) was designed for
it. When pounded into the ground or a road and loaded with the
cartridge, a man stepping on it would fire the cartridge. Also
useful for blowing the tires of trucks running over the device.
Nicknamed the "Castrator" by the troops.
The cartridge seen at the bottom is the wooden bulleted "practice cartridge". The live cartridge looked the same but had a steel bullet. |
This early version was not fitted with a spring snout, it has a solid brass mounting for a detonator. The aluminum tube adapter was used to attach safety fuze instead of a detonator. |
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| Switch, No. 10, Delay Mk. I | Switch, No. 12. Release, Mk. I |
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The switch on the top is the earliest type, the three pictured on the bottom are later manufacture. This delay used a corrosive liquid to eat through a wire holding the striker in the cocked position. The coloured tabs you see near the end of the switch denoted the nominal delay of the switch. Black = 10 min. Red = 19 min. White = 1 hr 19 min. Green = 3 hrs 10 min. Yellow = 6 hrs 30 min. Blue - 14 hrs 30 min. These are the average delay times at 77 degrees. The bottom switch is known as a "Signal Relay Incendiary and was designed for use on the US designed "Pocket Incendiary" |
This was an anti lift device to be used under antitank mines. The upper portion contains a small explosive charge which would cause the AT mine to detonate if someone attempted to lift it. |
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| Switch, No. 13, Pull/Pressure/Release Mk. I | Switch, No. 14, Charge fixing, Mk. I |
| A combination switch developed by MD1 near the end of WWII. This device while it worked well did not find favor with the troops who were quite satisfied with the earlier switches. | Designed to fire a nail into wooden hulled ships to hold Limpet mines in place. There was also a version that would fire a spike into a metal hulled vessel. |
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| Fog Signal | Imber Railway Switch |
| Two versions of the "Fog Signal". Made to resemble a piece of railway equipment, this chemical crush igniter would be attached to the rails and an explosive charge so that when run over by a train it would blow the rail and derail the train. | Designed specifically to be used on railways. This switch could be set to fire after a number, up to eight, trains had passed over it. |
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| Fog Signal | |
| Likely more rare than a live or deactivated fog signal, here is a dummy version. | |
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| Tire mine camoflage | Tire mine camoflage |
| This is the horse dung camoflage for the tire mine. | This is the rock camoflage for the tire mine. |
