vertical linearity control

vertical linearity control

[′vərd·ə·kəl ‚lin·ē¦ar·əd·ē kən‚trōl]
(electronics)
A linearity control that permits narrowing or expanding the height of the image on the upper half of the screen of a television picture tube, to give linearity in the vertical direction so circular objects appear as true circles; usually mounted at the rear of the receiver.