Magnetic tape drive
A magnetic tape drive (also called a transport, or unit) is the actual mechanical mechanism which handles a reel of magnetic tape (hub, motors, etc); it also includes a certain amount of electronics (e.g. usually the amplifiers which handle the signals from the magnetic heads are included in each drive).
Beyond that, what else is included all depends on the manufacturer, and often on the particular product line, though; how they paritition functionality, and how they pull out common sub-units to prevent un-needed duplication.
For example, in the DEC TU10 magtape drive/TM11 magtape controller system, not only is the magnetic tape controller separate from the drive, but the drives come in 'master' and 'slave' variants, with one master drive (which contains extra electronics) needed on each controller.