Definition of busy. busier. ; busiest. 1a : engaged in action : occupied She's busy studying. has enough work to keep him busy for a whileb : being in use found the telephone busy. 2 : full of activity : bustling a busy seaport.
It is considered a high quality tube, and is normally constructed from SAE 1020 or 1026 steel. Note that, technically DOM refers to the process by which the tube is finished after having started as an ERW tube. Technically, DOM is not a type of steel tube, but rather a process. As so often happen though - in common use the term has become accepted to mean a specific type of tubing rather than a process.
Modern vacuum tubes, mostly miniature style. In electronics, a vacuum tube, an electron tube, or just a tube (North America), or valve (Britain and some other regions), is a device that controls electric current between electrodes in an evacuated container. Vacuum tubes mostly rely on thermionic emission of electrons from a hot filament or a cathode heated by the filament.