Ancient Near East, Lehi's Journey
The Liahona was given by the Lord as a communicationsdevice for Lehi to determine the appropriate direction of travel. This device contained two pointers, only one of which was necessary to provide directional information. But the Liahona was more than just a simple compass in function, for it additionally required faith for correct operation. Since a single pointer always "points" in some direction, the additional pointer was necessary to indicate whether or not the first pointer could be relied upon. This proposed purpose for the second pointer conforms to a well-established engineering principle used in modern fault-tolerant computer systems called "voting," in which two identical process states are compared and declared correct if they are the same, and incorrect if they are different. Hence the second pointer, when coincident with the first, would indicate proper operation, and when orthogonal, would indicate nonoperation.
BYU ScholarsArchive Citation
Bunker, Robert L.
"The Design of the Liahona and the Purpose of the Second Spindle,"
Journal of Book of Mormon Studies: Vol. 3
, Article 1.
Available at: http://scholarsarchive.byu.edu/jbms/vol3/iss2/1