Electrodynamically producing ultrasonic waves

Electrodynamic transducing device including two staggerdly coils with a distance of staggering equal to a quarter of a wavelength of ultrasonic waves, the improvement of assuring unidirectional transmission characteristics of said transducer comprising:

• means for feeding said two coils separately with discrete HF current pulses and at a particular time difference of feeding of the respective two pulse signals, the time difference being equal to a quarter of the wavelength such that a reinforcing ultrasonic signal is produced in a direction away from the coil receiving said signal earlier in time the coil being displaced in that and complete cancelation of acoustic waves obtains in the opposite direction, whereby in case of equal pitch of said coils the HF signals are of equal contour but of opposite polarity while in case of opposite winding pitch the signals not only have equal signal contour but also the same polarity.