What does VVVF stand for?

A given signal's second harmonic is twice the given signal's fundamental frequency. Harmonics are generated when there are non-linearities in an amplifier (there are always non-linearities). The worse the non-linearities, the more harmonics. A signal at 27.5 MHz (approximate frequency for US citizen's band) would have a second harmonic at 55.0 MHz (on US channel 2!). Can you see why there might be problems? A CB operator might do well to place a low-pass filter on his radio.

It's commonly used for MP3 players, computer BIOS code and "thumb" drives. Originally developed in Japan by Toshiba, it has become quite popular for products requiring non-volatile erasable memory. Flash devices have a limited number of erase cycles (typically 10,000 to 1,000,000 cycles) so they're not as good a choice for applications in which the data changes constantly. However, since it has no moving parts (unlike a hard disk) it is an excellent choice for storing the operating code for small personal electronics like PDAs, cell phones, digital cameras, and the data in items like MP3 players.

The terminals of FETs are called gate, drain and source. You might be more familiar with bipolar junction transistors (BJTs), which have terminals called base, collector and emitter. FETs were conceptualized first, but BJTs were easier to produce and so developed sooner.

On December 12, 1901, a radio transmission received by Guglielmo Marconi resulted in the first transmission of a transatlantic wireless signal (Morse Code) from Poldhu, Cornwall, to St. John's, Newfoundland.