Abstract: A depth finder utilizing a CPU to control the function of various components including a transducer, receiver, and a liquid crystal display, allowing a user to select between fresh and salt water operational modes as well as between English and metric display units. The CPU is controlled by a keypad and varies the rate at which stored transducer data is transferred from the receiver to the CPU such that the data is always representative of a fixed depth increment in any operational mode.

Abstract: A liquid crystal display depth finder using a sonar transducer is provided with a plurality of input keys interfaced to a microprocessor with each input key being dedicated to a particular function or feature usable with the depth finder. The microprocessor is utilized to control the operation of the transducer and the display of the data generated thereby in accordance with the particular function or set of functions chosen by the operator and to manipulate programming stored within the depth finder which will enable a tutorial mode comprising alphanumeric information and command key indication such that an the user may determine how the machine is to properly function.