developed a different ERCLMD that worked through the principle of electrical resistance but was modified by the addition of an audible ‘marker tone’.
The principle of measuring root canal length by this device is based on the assumption that the low frequency oscillation, as produced by the resistance and capacity between the oral mucous membrane and the gingival sulcus, is the same as the frequency between the periodontal ligament (at the canal terminus) and the oral mucous membrane