Apparatus for controlling sonic energy distribution

Claim 1

An improved vehicle presence detection system comprising: transmitter means producing periodic pulses of sonic frequency and peculiar time duration; transducer means converting said pulses to emitted sonic energy pulses and respondingly generating electrical signals relative to received sonic energy including energy reflected from said vehicle; detector means operable when actuated to manifest a distinctive indication of vehicle presence; receiver means rendered responsive for a selected interval to said signals for actuating said detection means only when signals having a peculiar characteristic correlative to said pulses of sonic energy are received during said selective interval, wherein the improvement for projecting the emitted sonic energy in a peculiar controlled pattern comprises: wave guide means interposed at the output of said transducer means for modifying the propagation of sonic pulses, said wave guide means setting up substantially a line source of sonic energy for spreading said emitted sonic energy in a direction perpendicular to said line source such that an elliptical pattern of sonic energy is produced and said line source of sonic energy providing an operating pattern of at least a minimum intensity over said elliptical pattern.