Temperature stable ultrasonic delay lines

Claim 1

IN A SOLID ULTRASONIC DELAY LINE, AN ALKALI-LEAD-SILICATE GLASS DELAY LINE MEDIUM HAVING A TEMPERATURE COEFFICIENT OF TIME DELAY NOT EXCEEDING EIGHT PARTS PER MILLION PER *C., AN ATTENUATION NOT EXCEEDING 8X10**-3 DECIBELS PER CYCLE, AND BEING COMPOSED OF ABOUT 10-50% PBO, 0-10% CDO, 0-10% BAO, 0-20% BI2O3, THE TOTAL CONTENT OF PBO, CDO, BAO AND BI2O3 BEING ABOUT 20-50%, ABOUT 4-20% K2O IN WHICH UP TO 1/2 OF THE K2O MAY BE SUBSTITUTED BY AT LEAST 1 ADDITIONAL ALKALI METAL OXIDE IN THE INDICATED AMOUNT SELECTED FROM THE GROUP CONSISTING OF 0-4% NA2O, 0-3% LI2O, AND 0-24% RB2O, AND WHEREIN THE SUBSTITUTION IS ON THE BASIS OF 0.4 PART NA2O FOR ONE PART K2O, 0.3 PART LI2O FOR 1 PART K2O AND 2.4 PARTS RB2O FOR 1 PART K2O, THE CONTENT OF RECITED HEAVY METAL OXIDES VARYING IN INVERSE MANNER WITH THE CONTENT OF RECITED ALKALI METAL OXIDES, AND THE BALANCE OF THE COMPOSITION BEING ESSENTIALLY SILICA.