Abstract: Sonar echoes of length s/c (cos .theta..sub.i +cos .theta..sub.r)+T are slated by transmitting properly timed replicas of an illuminating signal from a number of projectors spaced along a cable of target length s. Because of the length of this cable, magnetic anomaly effects can be simulated by passing a current through a conductor within it.

Abstract: A system for detecting the presence of intruder targets in an area under ar surveillance and in which the number of normal targets may vary, including the processing of gated time sample receiver signals through a first monitoring circuit having a counter and comparator means to develop output signals representing deviation of actual time sample count from a normal reference count, and through a second monitoring circuit including additional counter and count trigger means for developing an alarm signal responsive to continued deviation of actual count from reference count over several actual counts in a time sequence of counts such that normal variation of target number will not produce an alarm signal.

Abstract: A sonar system having a transmitting transducer adapted for being moved ag a predetermined path, a transmitter for energizing said transmitting transducer, an omni-directional receiving transducer spatially disposed behind said transmitting transducer, a sidewardly and downwardly looking receiving transducer contiguously disposed with said omni-directional receiving transducer, a receiver connected to the output of said sidewardly and downwardly looking transducer, a series connected detector, differentiator, delay, and time base generator coupled to the output of said omni-directional transducer, and a readout connected to the outputs of the aforesaid receiver and time base generator.

Abstract: A sonar system having a sonar transmitter which is programmed to broadcast wo sets of several increasing frequency signals, with the frequency gap between each set thereof sufficient to cause them to distinguish between deep and shallow water targets, respectively. A heterodyne receiver receives target echoes of said sets of several frequency signals and converts them to two sets of identical frequency signals which are then readout as a single continuous target display signal.

Abstract: An electronic barrier utilizes a bifurcated beam of wave energy to establ a barrier area having a null between the forks thereof. Objects encroaching on said beam cause a portion thereof to be scattered in the foreward direction. Suitable receiver equipment located remote from the source of the bifurcated beam and responsive to the foreward scattered beam is connected to provide an indication of said encroachment.

Abstract: A sonar system having a transmitter for successively broadcasting a pair of coustical signals having different frequencies, a programmer for determining the times said pair of signals are broadcast, a receiver for receiving said pair of signals after they have been reflected from a target, a programmer for effecting the conversion of said received pair of signals into a continuous unitary electrical signal having variable consecutive time periods which alternately contain the respective frequencies thereof, and a readout for displaying said continuous unitary electrical signal.

Abstract: A sonar system for detecting and identifying objects laying on or submerged n a sea floor having a dual frequency transmitter and a dual frequency receiver for timely broadcasting and receiving a pair of relatively high and low frequency acoustical signals, respectively, in accordance with a predetermined timing program which facilitates the display and interpretation thereof.