Connecting rod 3 is connected by turning pairs A and B to link 2 of four-bar linkage CDEF and to slider 4. When crank 1 rotates about fixed axis C, slider 4 is almost stationary at the portion of the path a-a of point A that approximates a circular arc described from point B as its centre. Thus, slider 4 practically has a dwell.
$1645$SC,D$