Abstract: A safety system for automatically shutting off the power-take-off of a tractor in an emergency to thereby stop the machine being driven by the power-take-off. The system includes at least one machine sensor for detecting the presence of a foreign body adjacent a portion of the machine, and a shut-off, responsive to the sensor, for shutting off the power-take-off when the sensor detects the presence of a foreign body adjacent the machine. Sensors can also be provided to monitor the power-take-off shaft The sensors are preferably a photocell. The system optionally include an alarm that sounds when the sensor detects the presence of a foreign body adjacent the machine.