The lengths of the links comply with the conditions: A͞C=C͞B=B͞F=F͞A=a, D͞F=D͞C=b and E͞A=E͞D. When link 1 turns about fixed axis E, point B travels along straight line q-q which is perpendicular to ED. The mechanism always satisfies the conditions: D͞A×D͞B=a²-b²=const. The polar equation of straight line q-q is D͞Bcos(α)=(a²- b²)/(2E͞D)=const. Directions AB and CF are always mutually perpendicular.
$702$LW,GI$