System for redirecting output to either return bus or next module line upon the detection of the presence or absence of next module using ground line

Claim 1

A modular avionics system, for use in an aircraft computer and communication system of a type having an aircraft data distribution network therein, the modular avionics system comprising: a modular avionics system cabinet having first, second and third slots therein and further having a backplane therein interconnecting said first, second and third slots, said cabinet coupled with said aircraft data distribution network; said backplane having a first line disposed between and connecting said first slot and said second slot, and a second line disposed between and connecting said second slot and said third slot and a uni-directional return bus therein; a plurality of line replaceable modules, including a first line replaceable module disposed within said first slot and having disposed therein means for determining the presence or absence of another line replaceable module in said second slot, and means therein for directing an output from said first line replaceable module in response to a determination by said means for determining to either of said return bus or said first line; and, said means for determining the presence or absence of said another line replaceable module in each of said plurality of line replaceable modules comprises a plurality of buffers disposed within said each of said plurality of line replaceable modules, and a ground line extending from said first line replaceable module to said second slot, so that if said another line replaceable module is inserted into said second slot said ground line will be grounded.