An energy-efficient system for measurement of analog signals including one or more measuring units. Each measuring unit has a measuring probe which signal is processed by a modulator. All measuring units have identical modulators selected from the Time Encoding Machine family: Asynchronous Sigma Delta Modulator, Integrate And Fire Modulator and Integral Pulse Frequency Modulator. A signal from the modulator is processed by a delay circuit from which is optionally fed back to the modulator. Signals from the delay circuit and modulator are used to trigger a UWB pulse generator, which is optionally amplified and transmitted via transmission line or antenna. The delay circuit uniquely characterizes the measuring unit and enables the receiving unit to separate received signals from plurality of measuring units signals sent in an unsynchronized manner. The invention is useful for long term acquisition of analog signals, especially time varying signals such as biological signals.