Depth sounder digitizer

Claim 1

A water depth digitizer producing an averaged digital readout from a depth sounder producing acoustic ranging pulses in a plurality of depth sounding cycles and includIng a transducer producing receive signals representing the return of the reflected acoustic ranging pulses comprising: a source of clock pulses, a digital counter driven by said source of clock pulses for producing a digitized readout averaged over said plurality of depth sounding cycles and representing water depth, means for starting said digital counter in response to the occurrence of each said acoustic ranging pulses, means for stopping said digital counter in response to each of the receive signals occurring after each acoustic ranging pulse so that said digital counter produces an accumulated count of said clock pulses during the time intervals between each of said acoustic ranging pulses and their respective receive signals, said accumulated count representing water depth averaged over said plurality of depth sounding cycles, a reset circuit for said counter, and means for detecting the sequence of occurrences of said acoustic ranging pulses and the respective reflected receive signals and for enabling said reset circuit when a receive signal produced by the reflection of an acoustic ranging pulse is not received before the next occurring acoustic ranging pulse, the reset circuit setting said digital counter to zero to indicate that an inaccurate sequence of water depth soundings has occurred.