1. The method of detecting His signals at the surface of a patient comprising the steps of (a) acquiring a surface ECG signal at a plurality of external locations on the chest of the patient; (b) digitizing the acquired ECG signals by continuous sampling at a rate greater than the Nyquist rate; (c) storing said digitized ECG signals; (d) selecting one of said ECG signals to be a reference channel, with the remaining ECG signals referred to as input channels; (e) calculating a feedback coefficient u.sub.j for each of a plurality of sample points j in a cycle of the ECG signals; (f) there-after adaptively filtering at least a portion of each cycle of each of the input channels including the steps of (i) conducting a first pre-updating of a weight matrix associated with sample point j for each input channel with reference to an input channel signal to one side of sample point j, (ii) conducting a second pre-updating of the weight matrix associated with sample point j for each input channel with reference to an input channel signal to the other side of sample point j, (iii) calculating an output signal at sample point j by multiplying each weight matrix at sample point j by the associated input channel at sample point j and surrounding points as determined by the length of each weight matrix and totalling the products of said multiplication, (iv) conducting a final updating of each weight matrix associated with sample point j with reference to the output calculated in step iii, the feedback coefficient u.sub.j and the reference channel signal and input channel signals at sample point j, and storing said weight matrices for use in a subsequent cycle, (v) repeating steps i-iv sequentially for each sample point j in a particular cycle, and (vi) repeating steps i-v sequentially for each cycle of the acquired ECG signals, and (g) displaying the output signal to give a reading indicative of the patient's electrocardiographic potential.