Abstract: An undersea communications system in which a message is converted to a redundant fixed-length data packet and transmitted acoustically as a quadrature phase-keyed signal in a frequency band with a continuous pilot signal at a frequency closely adjacent to the frequency band. A receiver uses the received continuous pilot signal to Doppler compensate the incoming quadrature phase keyed signal by estimating any Doppler distortion in the received pilot signal. The resultant redundant signals are then robustly processed coherently and jointly by the adaptive decision feedback equalizer and decoder to provide the original transmitted data.

Abstract: A crosspoint analog data selector for coupling data received on a predetened number of input channel lines onto a predetermined lesser number of output channel lines. The crosspoint analog data selector includes a selector section and a control section. The selector section includes two or more crosspoint switch sections, each crosspoint switch section including a predetermined number of input terminals and a predetermined number of output terminals. Each output terminal is individually energizable. Each input terminal is connected to a different input channel line, such that none of the input channel lines are connected to input terminals of multiple crosspoint switch sections. Each output terminal is connected to one of the output channel lines such that each output channel line is connected to an output terminal of each of the crosspoint switch sections.