Did You Know...
...that Thomas Edison's patent application on his phonograph was approved by the Patent Office in just seven weeks? In contrast, it took Gordon Gould, the inventor of the laser, 30 years to obtain his patent -- finally awarded in 1988!
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| Number | Title | Issue Date |
| 5680074 | Tube amplifier having specific configuration with four tubes There is provided a tube amplifier comprising a first vacuum tube K3 having a plate applied with a positive voltage and a cathode applied with a negative voltage by a first resistor, a second vacuum tube K4 having a grid connected to the cathode of the fi... | 10/21/1997 |
