Apparatus for preventing latch up of two systems which are connected electrically to each other and which have a respective independent power supply

An apparatus for preventing latch up of first and second systems which are connected electrically to each other and which have a respective independent power supply, at least one of the first and second systems being a computer system, said apparatus comprising;

• a buffer unit having a signal lines adapted to be connected electrically to the first and second systems to permit signal transmission between the first and second systems;
• and
• a buffer control unit connected electrically to said buffer unit and adapted to be connected electrically to the power supplies of the first and second systems, said buffer control unit being adapted to detect voltages of the power supplies of the first and second systems and disabling said buffer unit so as to disconnect the first and second systems from each other when the voltage of the power supply of any one of the first and second systems is not within a predetermined range;
• said buffer control unit includes a first detecting circuit for generating a first control signal when the voltage of the power supply of the first systems is not within the predetermined range, and a second detecting circuit for generating a second control signal when the voltage of the power supply of the second system is not within the predetermined range;
• and
• said buffer unit includes at least one buffer circuit having a disable input terminal, and at least one control gate having a first input terminal connected electrically to said first detecting circuit, a second input terminal connected electrically to said second detecting circuit, and an output terminal connected electrically to said disable input terminal of the buffer circuit, said control gate generating a disable signal at said output terminal thereof so as to disable said buffer circuit upon reception of at least one of said first and second control signals from said first and second detecting circuits.