Yamaha Drums is a subsidiary of the Yamaha Corporation founded in 1967. The company manufactures acoustic and electronic drum kits as well as percussion instruments, marching band equipment, and drum hardware.

Source Wikipedia: http://en.wikipedia.org/wiki/Yamaha_Drums

DTX electronic drum is the line of electronic-MIDI drum and percussion sets manufactured by Yamaha. The DTX Trigger System is a custom drum module which can be used to trigger sounds with acoustic drums (best demonstrated by drummer Akira Jimbo). A modified version of the DTX kit can be found in 2 drumming games: MTV Drumscape (which is not considered a true ‘game’) and the much more popular Drummania.

For the consumer market, there are three models:

DTXplorer, a set of “low end” electronic drum, though still pricy when compared to other MIDI-capable electronic drums. It features five single zone pads and two cymbal pads.
DTXpress, now in its fourth incarnation, is the mid range, and still offers very good quality. It consists of one 3-zone snare, three one-zone pads, one hi-hat pad, and two cymbal pads.
DTXtreme, now in its third incarnation, is the highest end DTX drum set, and aside from offering even more drum sounds (and more realistic ones too), it is also capable of plugging in extra drum pads. Additionally, the electronic drum pads can be multizoned too, as best to imitate a real acoustic drum.

Yamaha also announced in November 2009 the DTX MULTI-12 percussion pad set. The DTX MULTI-12 has 12 pads capable of finger, hand or stick triggering, and includes 1,277 voices for drum, percussion or melodic tone generation.

Source Wikipedia: http://en.wikipedia.org/wiki/Yamaha_DTX_series