Pinions 1 and 2 rotate about fixed axes B and A. Link 3 slides along axis C-C in guides a-a. Pinions 1 and 2 have the same number of teeth and mesh with each other and with the upper and lower gear racks b of link 3. When pinion 1 rotates counterclockwise, link 3 travels to the right; when pinion 1 is reversed, link 3 travels to the left.
$2346$SG,4L$