Patent ID: 8558415

Claim:
A safety device comprising: a controller which generates a control signal for controlling a controlled apparatus; and a safety function unit, connected to the controller, which executes a predetermined safety function, wherein the controller includes: a unit which selects a category for identifying a safety function unit which should be connected, a unit which transmits to the safety function unit a reference signal for generating a category identification signal which enables identification of a category, the category identification signal being returned from the safety function unit to the controller, a unit which, based on the category identification signal returned from the safety function unit, determines whether or not the category of the connected safety function unit coincides with the selected category, and outputs the result of the determination, and a unit which, in the event that the result of the determination is such that the category of the connected safety function unit and the selected category do not coincide, prohibits the output of the control signal, wherein the reference signal is a pulse train having a predetermined frequency, wherein the safety function unit includes an operation unit which, based on the reference signal transmitted from the controller, generates the category identification signal in accordance with the category of the safety function unit, and returns it to the controller; and wherein the operation unit includes dividing means for receiving the pulse train and dividing it in frequency.