Apparatus for indicating the farthest advance position of a

Abstract

Apparatus for indicating the farthest advance position of a bi-directionally movable medium is provided with a pulse generator mechanically coupled to the medium to generate pulses corresponding to incremental movements of the medium in either a first or second direction. The actual direction in which the medium moves is represented by respective first and second signals. A counter incrementally changes its count in response to each generated pulse when the medium moves in, for example, the second direction, and the counter reverses the direction in which it counts when the medium moves in the first direction following medium movement in the second direction so that the counter incrementally is restored to an initial count. Once the initial count of the counter is restored, an output farthest advance signal is produced indicating that the medium has reached its farthest advance position. In one embodiment, the apparatus is used to indicte the farthest advance of a movable web. When the web is reversed, the counter is decremented from an initial predetermined count. When the web subsequently is moved forward, the counter then is incremented. Once the web reaches the farthest advance position previously occupied prior to reverse movement thereof, the counter concurrently reaches its initial, predetermined count.