The DX11 is a 4-operator FM synthesizer. In contrast to previous DX-series synthesizers, the DX11 is 8-part multitimbral. It is the keyboard version of the TX81Z, which was released first. It allows the use of non-sine operator waveforms, which makes it possible to create richer sounds than those available to sine-only 4-operator synths.
Like the TX81Z, YS200, and TQ5, the sound engine is based on the Yamaha YM2414 chip.
The RAM battery is a CR2032 that is soldered to the circuit board, so it's difficult to replace. Typically the battery is desoldered from the board and replaced with a battery holder so that future replacements are easier.
To perform a factory reset, turn the power on. Press and hold the [EDIT] button, then the  button, then the  button. Release all three buttons. Press the [YES] button. Turn the power off and then back on.
A Japanese variant of this is called the "V2" and is the same synth with a different name. That name was not used outside of Japan due to the association with the V-2 rockets used by Germany in Word War II.
Year Released: 1988
Keyboard: 61 keys with velocity and aftertouch
Polyphony: 8 notes
Multitimbral: 8 parts
Preset Patches: 128
User Patches: 32
User Performances: 32
Screen: 16 x 2 character backlit LCD
Power Consumption: 10 watts
Dimensions: 901 mm x 298 mm x 63 mm
Weight: 7.0 kg
Yamaha DX11 Set 48 Taster komplett ($18.75)