Abstract: A safety device is provided for the operation of small presses, spot welding machines, etc. The device is characterized by the use of a probe or sensor whose movement, if obstructed, prevents closing of an electrical circuit which activates the punch or ram of the press. Means are provided for minimizing or eliminating bounce or vibration of the sensor to avoid erratic operation of the device and the press. Provision is also made for rendering the device "fail-safe" under certain conditions, including failure of internal parts of the device or improper usage of the device by the operator. Economies in manufacture of the device are effected by the improvement of certain parts and elimination of other parts of previously used devices of a similar nature and construction.