Switch-controlled security assemblies (20, 76) are provided which are especially designed for use with cargo enclosures (40), in order to detect any unauthorized opening of the cargo doors (38). The assemblies (20, 76) include one or more switch assemblies (26, 28) each having a switch member (44) and an associated shiftable component (46). In preferred forms, the switch member (44) includes a pair of switch elements (50, 52) and a body (54) movable between a first position in simultaneous electrical contact with the elements (50, 52), and a second position out of such simultaneous contact. The body (54) and components (46) are magnetically coupled such that movement of the component (46) during unauthorized opening of door (38) effects corresponding movement of the body (54), in turn actuating an alarm controller (30).