In Triple rocker mechanism, one link is fixed while the other three oscillates.
It is a non grashof linkage for which the sum of the lengths of the shortest link and the longest link is greater than the sum of the lengths of the other two links.
s + l > p + q
s = length of the shortest link
l = length of the largest link
p and q = lengths of the other two links
All the Triple rocker mechanism inversions are triple rocker only.