Abstract: Each ultrasonic transducer in a plurality provides a particular signal having characteristics related to the heart rate of an associated fetus. Each particular signal is processed in an associated labor room monitor and modulated on a different carrier frequency for transmission on power lines in the hospital. At a remote location, a nurses station power unit is modular with nurses station monitors. The line signals are individually demodulated in an associated one of the nurses station monitors to provide an indication of heart rate. Alternatively, the transducer assemblies can be coupled to delivery room monitors to provide an indication of heart rate.The transducer assemblies are uniquely shielded to inhibit interference of spurious low frequency signals with the particular signals. The particular signals are partially detected in the transducer assemblies so that the assemblies can be used with both the labor room and delivery room monitors.