AN APPARATUS FOR SIGNALLING THE OPERATOR OF A COTTON HARVESTER THAT A PREDETERMINED QUANTUM OF GREEN COTTON BOLLS HAVE BEEN COLLECTED IN A BOLL COLLECTING CHAMBER OF THE COTTON HARVESTERM THE CHAMBER HAVING A HINGED DISCHARGE DOOR ON WHICH COLLECTED GREEN BOLLS LIE, THE DOOR BEING BIASED IN A CLOSED POSITION BY A RESILIENT MEMBER ARRANGED TO PROVIDE A CLOSING FORCE TO THE DOOR SO THAT THE DOOR WILL ASSUME A SLIGHT PREDETERMINED DISPLACEMENT TOWARED THE OPEN POSITION WHEN THE BOLL CHAMBER IS FILLED TO CAPACITY, AN ELECTRIC SWITCH DISPOSED TO SENSE THIS DISPLACEMENT AND THEREUPON TO ACTUATE CLOSING AN ELECTRIC CIRCUIT WHICH ENERGIZES A SIGNALING DEVICE PLACED WITHIN SENSORIAL RANGE OF THE OPERATOR.