The original text clearly had the plural devices here in Alma 46:10. In the 1841 British edition, the typesetter accidentally replaced the plural with the singular device; the LDS text has continued with the singular device in this passage. Yet this change is inconsistent with the rest of the Book of Mormon text:
In other words, the rest of the Book of Mormon text has only the plural form devices, just as the original text had here in Alma 46:10.
Summary: Restore the plural devices in Alma 46:10, the original reading; elsewhere the text has only the plural form for this word.