Security device prohibiting the function of an electronic data processing unit after a first cutoff of its electrical power

A security device adapted to be connected to a power supply and being operative connected for (1) prohibiting execution of at least one function of an electronic data processing unit (2) after a first cutoff of its supply voltage even in the case of a resumption of supply voltage, comprising:

• first circuit means (8) connected for operatively functioning only once in the course of a period beginning at the instant (T.sub.0) of a first connection to voltage by the power supply (3), and ceasing its functioning prior to the instant (T.sub.2) of a first cutoff of this power supply, first means having an output (9) and furnishing at said output (9) in the course of this period, a signal characteristic of the functioning of said first means;
• second circuit having at least one input and at least one output (17), said means (10) one input being connected to the output (9) of the first means (8), said second input means being operatively connected for memorizing a characteristic signal from the instant (T.sub.0) of first connection to said voltage until the instant (T.sub.2) of a first cutoff, said second means (10) being connected via one output (17) to an electronic data processing unit (2) and furnishing at said output (17) an inhibiting signal having a first level that authorizes the function of the unit, from the instant (T.sub.O) of the first connection to voltage until the instant (T.sub.2) of the first cutoff, said inhibiting signal having a second level that prohibits said execution of said function beginning at the instant (T.sub.2) of the first cutoff, this inhibiting signal maintaining this second level even in the case of a resumption of voltage of the power supply.