Remote monitoring of biological signals such as ECG waveforms, in which an FM encoded version of an ECG waveform is transmitted from a patient's home to a central station where it is analyzed to estimate local frequencies at many more time points than the zero crossovers of the FM signal. A plurality of ECG waveforms is encoded in a composite FM signal any one point of which can represent at the same time a number of ECG waveforms. The composite waveform is analyzed at the central station to extract and reconstruct the individual waveforms by separation in the frequency domain.