Abstract: An electronic device for monitoring the insertion or travel of the filling or weft thread on an air jet weaving machine or loom which comprises at least one air jet arranged at the picking side of the machine, and a lathe or sley beam with thereon fixed lamellae forming a reed. The device comprises a tactile weft thread travel sensor arranged at the weaving machine upstream of said air jet, a start pulse generator controlled by the weaving machine, an optoelectrical sensor located near the end of the reed adjacent the weft receiving means, and electronic circuitry controlled by said start pulse generator and optoelectrical sensor for producing an activating signal defining the time interval during which the weft thread travel is monitored.