Anti-streptolysin O (ASO) is an antibody often found in the blood of people who have suffered a streptococcus infection. A blood test, known as the anti-streptolysin O titre, is sometimes used to test for the presence of this antibody in the blood. This test is considered useful because certain health conditions, such as rheumatic fever, usually only occur in people who have recently suffered or are suffering a streptococcus infection.
On December 26, 1933, he was awarded four patents for FM radio (The other two were applied for in 1927 and 1930, but weren't for wide-band). He discovered in early 1934 that his invention was almost free of static. Armstrong took a few more years to give FM high fidelity, but by 1938 or 1939 he had improved FM to the point that it was our FM radio, minus the stereo sound.
One of the first developments in the early 20th century was that aircraft used commercial AM radio stations for navigation. This continued until the early 1960s when VOR systems became widespread. In the early 1930s, single sideband and frequency modulation were invented by amateur radio operators.