Digital ultrasonic delay line

Claim 1

IN COMBINATION, A FLAT PLATE-TYPE SOLID DELAY MEDIUM HAVING SIGNAL INPUT, OUTPUT AND REFLECTION FACETS ARRANGED ABOUT THE PERIPHERY THEREOF AND SO DISPOSED THAT THE SIGNAL STRIKE ANGLES ARE AT LEAST EQUAL TO THE CRITICAL ANGLE OF THE DELAY MEDIUM, THE FLAT SURFACES OF SAID PLATE COMPRISING THE MAJOR PLANES OF SAID DELAY MEDIUM, THE INPUT, OUTPUT AND REFLECTION FACETS AND THE MAJOR PLANES BEING POLISHED SURFACES, SIGNAL INPUT AND OUTPUT TRANSDUCERS MOUNTED ON SAID INPUT AND OUTPUT FACETS RESPECTIVELY FOR VIBRATION IN THE THICKNESS-SHEAR MODE PARALLEL TO SAID MAJOR PLANES, SAID TRANSDUCERS EXTENDING SUBSTANTIALLY FROM ONE OF THE MAJOR PLANES TO THE OTHER, AN ACOUSTIC ABSORBER ADHERED TO AND SUBSTANTIALLY COINCIDENT WITH SAID INPUT TRANSDUCER AND AN ACOUSTIC ABSORBER ADHERED TO AND SUBSTANTIALLY COINCIDENT WITH SAID OUTPUT TRANSDUCER, EACH OF SAID ACOUSTIC ABSORBERS HAVING A MECHANICAL IMPEDANCE SUBSTANTIALLY MATCHING THE MECHANICAL IMPEDANCE OF EACH RESPECTIVE TRANSDUCER.