Edwin K. Shenk

Dual burst, wide range sonar system

A sonic ranging system providing at least two bursts of sonic energy of unequal duration directed toward a subject with the time interval between the bursts being no less than the round-trip time for the maximum range at which a subject is to be detected by the preceeding burst includes a receiver which is blanked for a time related to the duration of each burst such that the shorter burst is used to detect very close subject distances and the longer burst employed for further distances. Preferably, the range detected by only one of the bursts is automatically utilized, depending upon whether the subject range is greater or less than a given distance.