Chapter 12 - Clocks and Associated Devices - Automatic Latitude-Adjustment Devices (A.L.A.): Magnetic A.L.A.Chapter 12 - Clocks and Associated Devices - Prevent-Stripping Equipment (P.S.E.) (Geheimhalteeinrichtung)
GERMAN UNDERWATERS ORDNANCE MINES
Chapter 12 - CLOCKS AND ASSOCIATED DEVICES
AUTOMATIC LATITUDE-ADJUSTMENT DEVICES (A.L.A.)
ELECTROMAGNETIC A.L.A. (Figure 301)

The needle consists of an aluminum drum, mounted horizontally and fitted with a mag-netic belt which is magnetized diametrically. It is placed between two sets of vertical pole pieces which conduct the vertical component of the earth's field thoruh the needle. The needle G thus tends to rotate counter-clockwise as a result of the RED field effect.

A separate local magnet J, would with a coil, is also fitted to the unit. Its polarity is such that it puts out a BLUE magnetic field which tends to rotate the needle clockwise. This BLUE field is stronger than the earth's field; and, as a result, the needle rotates clockwose to its limit stop.

A contact K is mounted on the drum, and two vertical wires are placed in such a po-sition that clockwise or counterclockwise rotation of the drum causes K to make contact No. 2 or No. 1 respectively. Thus, contact No. 1 becomes the RED contact and contact No. 2, the BLUE contact; and, since the field of the local magnet is stronger than that of the earth, the needle will make contact K2 when the mine is laid.

When the unit is energized by the battery, current through fuse R (figure 302) ener-gizes the latitude-adjuster coil S and thermistor M. S is wound on the local magnet and is energized so that the field produced will be opposite to that of its core (i.e. the local magnet). The field produced by energizing S is stron enough to overcome the BLUE field of a local magnet, causing the needle to break contact K2, thereby breaking the electro-magnetic field of S. Since the residual magnetism of the local magnet is strong enough to swing the needle back again, contact K2 is again made and S re-energized.

This pulsing, or deperming, continues until the residual magnetism of the local magnet is no longer capable of making switch K2. The process is assisted by the heating of ther-mistor M, whose decreasing resistance allows it to pass more current, thereby decreas-ing the pulsing current through S.

Figure 301– Electromagnetic A.L.A. Component Parts

Figure 302 – Electric A.L.A. Circuit

Chapter 12 - Clocks and Associated Devices - Automatic Latitude-Adjustment Devices (A.L.A.): Magnetic A.L.A.Chapter 12 - Clocks and Associated Devices - Prevent-Stripping Equipment (P.S.E.) (Geheimhalteeinrichtung)