FAULT TOLERANT SUBRATE SWITCHING SYSTEM

摘要

A plurality of input signals are switched in an apparatus including redundant switching planes and hardware for receiving an output signal from each of the redundant switching planes. Each switching plane is for switching the plurality of input signals, and each switching plane includes at least two switching modules, each switching module being connected to receive a subset of the input signals directly from an input signal source coupled to the apparatus. Each switching module is further connected to receive a remaining subset of the input signals from remaining switching modules on the same switching plane; and each switching module generates an output signal having components selected from the plurality of input signals. To improve performance in the event of a double fault, each switching module detects whether any of the remaining switching modules on the same switching plane are faulty. In response to any such detection, the switching module substitutes a signal representing a logical zero for those portions of the output signal that are selected to include one or more components from the faulty switching module. Also, when the means for receiving the output signal from each of the redundant switching planes detects that each of the output signals received from corresponding switching modules in the redundant switching planes is invalid; it responds by logically OR'ing the received output signals together. In this way, the likelihood of recovering a valid output signal is increased. In one embodiment of the invention, each switching module is a subrate switching module.