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| GERMAN UNDERWATERS ORDNANCE MINES |
| Chapter 4 - CONTACT AND MOORED INFLUENCE MINES |
| THE GERMAN EM (EINHEITSMINE) MINE SERIES |
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The EMA Mine. The EMA was developed during World War I and was the first German mine with a chemical-horn firing system. Accordingly, to differentiate it from the pendu-lum-type mines then in use, it was designated Elektrische Mine Type A. Its production was discontinued at the close of the war. Its apperance in World War II is accounted for by the fact that stocks remained on hand in 1939. |
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The mine existed in two models, one for laying by surface craft and the other by sub-marine. Only the surface craft type was laid in World War II, since the other type requi-red specially fitted submarines which were not available. |
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Figure 5 – EMA Mine Afloat |
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Description of Case. |
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Shape |
Two hemispheres, joined by a 12-in. cylindcrial mid-section. |
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Material |
Steel |
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Diameter |
34 in. |
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Length |
46 in. |
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Charge |
330 lb. block fitted hexanite |
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Description of External Fittings. |
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Horns |
Five: one in center of upper hemisphere; four, equally spaced, around upper hemisphere |
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Arming switch and booster release |
On mid-section, secured by keep ring |
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Detonator carrier mounting |
In bottom center of case |
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Mooring bracket and white metal mooring switch |
Bolted to two lugs on lower hemisphere |
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Mooring pulley and "come-along" |
Attached to extension of mooring bracket |
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Depth taking hydrostat |
Bolted to extension on mooring bracket |
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Figure 6 – EMA/EMB Mine |
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Two pair of electrical leads extend from the white metal mooring switch, one set to the detonator carrier, the other to the arming switch. |
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Operation. Mine taken depth by hydrostat. Separation of the anchor and case with-draws a safety pin from the arming switch and booster release, making the circuit from the horn batteries to the detonator and allowing the booster to drop over the detonator. Mooring tension extends the spindle of the white metal mooring switch, arming the circuit of the internal horn to arm the mine. |
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