Patent ID: 6351828
Filing Date: 2002-02-26
Classification: B60R

Abstract:
A safety device for a diagnostic terminal for a distributed computer network containing at least two nodes and a common communication bus for the computer network, which diagnostic terminal includes a first set of contact pins for access to the communication bus and is connectable to an external diagnostic equipment for performing diagnostics on the nodes within the computer network, the safety device comprising:switches which, in a first stable position, connect the first set of contact pins to the communication bus and, in a second stable position, disconnect the first set of contacts from the communication bus; and a signal evaluation circuit connected to the first set of contact pins and arranged to enable detection of a predetermined signal state from the diagnostic equipment at the first set of contact pins and, when a predetermined signal state occurs, causes the switches to switch from the second stable position to the first stable position to connect the first set of contact pins to the communication bus, so that the diagnostic equipment connected to the diagnostic terminal may obtain direct access to the communication bus, the diagnostic equipment applying the predetermined signal state to a second set of contact pins connected with said first set of contact pins when the diagnostic equipment is connected to the diagnostic terminal and the signal evaluation circuit including a detection device which, dependent on a specific voltage level within a predetermined voltage range applied on at least one of the first set of contact pins, will activate the switches and at least two comparators each comparing the voltage applied on at least one of the first set of contact pins with first and second reference voltages, respectively, which first and second reference voltages are obtained from a voltage divider.