The lengths of the links comply with the conditions: A͞B=B͞C and D͞C=D͞A. At the extreme positions (dead points), socket a' and pin b' abut against stops a and b of fixed link 4. As a result, uncertainty of motion of the mechanism is eliminated. The dimensions A͞a and A͞b equal: A͞a=A͞B+B͞a̕ and A͞b=A͞B-B͞b̕.
$545$LW,4L$