Push-button 1 slides in fixed guides a-a and is connected by turning pair B to pawl 2 which engages the teeth of four-tooth ratchet wheel 3. Ratchet wheel 3 rotates about fixed axis A and is rigidly attached to (or integral with) square link 4. When push-button 1 is pressed, ratchet wheel 3 is turned 90°. Flat springs 5 engage the sides of link 4 to hold the ratchet wheel in each indexed position.
$2701$RG,4L$