Occasions still exist for a designer to select a purely mechanical means to realize some special motion types, such as exact dwell at limit positions of the output link. This happens particularly when the design emphasis is placed on highly reliability, high operation speed and low cost. In this paper, a new principle and synthesis method to develop a class of linkages which enable a relatively long exact dwell at 1-2 limit positions of output link are presented. It will be shown that with this new class of linkages, a longer exact dwell can be realized in comparison with those existing classes of linkages including cam mechanisms. Furthermore, a spatial input and output motion can be realized. Application of such a kind of linkage has been found in a package packing machine.