Abstract: In a hay baler, or the like, of the type which compresses loose product into bales which are moved along a controlled path to be tied with a binding such as twine. A device for sensing malfunction of the tying apparatus and signaling that malfunction to the operator, or alternatively, automatically shutting down the baler in response to the signal in which each sensing element comprises a series of bridge like members, each one of which is disposed in a longitudinal path down stream of the knotter devices in the direction of flow of the bales, and which are tied to the knotter devices by linkage which transmits motion of the knotter device to the sensing elements. Each sensing element is rotatably mounted to the baler frame and will move in response to movement generated by a malfunction in the corresponding knotter device. The movement of any sensing element trips a signal or shut down, at the operator's option.