An digital interface and receiver for time-of-flight level measurement and pulse-echo ranging systems. The memory includes a first count detection circuit for detecting an access frequency with respect to memory cells, a second count detection circuit for detecting an access frequency of each of memory cell blocks and a third count detection circuit detecting a no-access frequency resulting in an imprint. Wire members having a predetermined outer diameter are wound in a predetermined lead and pitch to provide a large number of helical wire members in such a fashion that a diameter of a helix is about twice the outer diameter of the wire members, crests and troughs have substantially a similar shape, and each trough is positioned outside the center of helix.