Abstract: An apparatus for acoustically detecting the location of a distal end of a tube relative to a body conduit into which the tube is being inserted is provided. The apparatus including a speaker positioned to generate a sound pulse in the tube and a sensor for detecting a sound pulse in the tube at a distal position relative to the speaker, and for generating a signal corresponding to the detected sound pulse.

Abstract: In one embodiment, a method for DMR includes generating first tracking reports of first data units received at one or more receptors from one or more remote units, generating second tracking reports of first data units received at one of one or more centrals, and generating delivery reports of second data units extracted at the central from the first data units received at the central. The method includes, using the delivery reports, identifying missing second data units that should have been received at the central, but were not. The method includes, using one or more of the tracking reports, mapping the missing second data units to one or more first data units and determining a best source for retransmission of the first data units mapped to the missing second data units. The method includes generating a retransmit request for the first data units mapped to the missing second data units and communicating the retransmit request to the best source.