which are produced in the interrogating equipment by a set of circuits which have not been shown as they do not constitute part of the invention are respectively applied to n logic circuits 3l 3n implemented in a technology which is not subject to the self powering phenomenon such as for example ttl technology and are powered by a reference voltage vap1 obtained downstream of a fuse 4 provided on this item of equipment the fuse being supplied at its upstream end with a direct current voltage v the interrogation signals obtained at the output of these logic circuits 3l 3n are applied respectively to the responding items of equipment 2l 2n via 34 n 34 leads 5l 5n should the fuse 4 on the equipment board blow with the result that these circuits are no longer powered a determined voltage level that is characteristic of this condition is obtained at the output of these circuits inversely the answers or responses from the responding items of equipment 2l 2n are directed to the interrogating equipment over a common transmission support which is here constituted by a 34 p 34 line parallel bus 6 and are applied at their input into this equipment to a logic circuit 7 which can be implemented in a technology that is or which is not subject to the self powering phenomenon the problem here is in fact less acute than is the case for access to the common bus and which is powered just like the logic circuit 3l 3n in other words powered only in the absence of cutting off of the power by the voltage vap1 the logic circuit 7 includes the same number of individual identical logic circuits as the number of lines on the bus each.