The world's highest recorded surface temperature is 56.7 Â°C (134 Â°F) measured at Greenland Ranch in Death Valley, California, USA on July 10, 1913. The mean temperature in Dallol, Ethiopia is 34.4 Â°C (94 Â°F), the highest annual average temperature on earth.
The Wave System III is made in Columbia South Carolina. The Bose A20 and A20 Bluetooth headsets are made in the United States. The US made Bluetooth Headphones they provide are the the most advanced BoseÂ® aviation headset yet, and they are still US made. The A20Â® Aviation Headset is used primarily in the aviation industry.
The Early Days. 1919 headphones originated from the earpiece, and were the only way to listen to electrical audio signals before amplifiers were developed. The first truely successful set was developed by Nathaniel Baldwin, who made then by hand in his kitchen and sold them to the U.S. Navy. 1937 German company Beyerdynamic invented and produced the first dynamic headphones, the DT-48, which are still in production today.