Most of the published work on massive redundancy makes one crucial assumption: the redundant modules are synchronized. There are three ways of achieving synchronization in redundant systems-independent accurate clocks, a common external reference, and mutual feedback. The use of a common external reference is currently the most widely used technique, but suffers from vulnerability to common-point failures. We introduce a novel mutual feedback technique, called "synchronization voting," that does not have this drawback. A practical application of synchronization voting is described in the appendix—a fault-tolerant crystal-controlled clock.