A fault tolerant modem system is provided according to some embodiments of the invention. A modem can include modulators and/or demodulators that provide redundancy in the event one of the modulators and/or demodulators fail. Connectivity between modulators and demodulators, for example, can be used to propagate TDMA timing to connected modulators and/or demodulators. Moreover, redundancy can be provided using modulators and/or demodulators with three or more input/output ports.