An ECG system can therefore be built into a chair, a mattress, or clothing for instance. The DRL circuit improves the sensor signal/noise ratio enormously. In the example in Figure 1, EPIC sensors are mounted on a chair back such that the electrodes touch the clothing on the subject's back when resting normally against the back of the chair. The generated DRL signal is connected to a piece of conductive material placed either on the seat of the chair, or at the bottom of the chair back, contacting the subject's clothing in the normal sitting position. Copper-coated nylon fabric is one possible material suitable for the DRL coupling material, but other conductive materials may be equally successful. A thin, non-conductive material such as a cotton fabric may be used to cover both the sensors and the DRL coupling fabric if required, for instance when building the sensors into a seat. Consideration must be given as to how material will reduce the coupling capacitance between the sensor and the subject, or add additional noise to the signals through static charging effects.