Abstract: An imaging sonar system is disclosed comprising a transmitter, a receiver, and a rotatable transducer coupled with the transmitter and receiver for generating sound waves and for detecting echoes therefrom. Drive means are provided for rotating the rotatable transducer. Transducer position sensing means are provided for sensing the rotary position of the transducer. Analog to digital converter means are coupled with the receiver for converting receiver emitted signals into digital form. Serial access memory means are provided entering into storage receiver emitted signal data in digital form at a preselected rate and for withdrawing from storage receiver emitted signal data at a rate different than the predetermined rate. Write and read control means are also provided for respectively entering digital data into and recalling digital data from the memory.