Theory of Machine
The mechanism consisting of three turning pairs and one sliding pair, is called a

Whitworth quick return motion mechanism
All of these
Crank and slotted lever quick return motion mechanism
Single slider crank chain

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Theory of Machine
The contact ratio is given by

(Length of the path of approach)/(Circular pitch)
(Length of the arc of contact)/(Circular pitch)
(Length of the arc of approach)/cosφ
(Length of path of recess)/(Circular pitch)

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