Abstract: An electro-mechanical displacement transducer comprises a probe on which shunt capacitance and series inductance are uniformly distributed to form a distributive constant circuit. The probe includes a nonconductive central member coaxially covered by cylindrical inner and outer conductor members insulated and separated from each other, at least one such conductor member being a coil. A pulse source connects to the sending end of the probe and a circuit element having an impedance related to the characteristic impedance of the distributed constant circuit connects the inner and outer conductor members at the receiving end of the probe. In use, the probe is displaceable with respect to a wave reflecting means such that the duration, between the time when a pulse is applied to the sending end of the probe and the arrival of the reflected wave at the sending end of the probe, varies in direct proportion to the relative displacement of the probe and wave reflecting means.