What is "dual-voltage"

Dual-voltage could refer to:

• Multi-system (rail), in which the trains are able to operate on more than one railway electrification systems
• Dual-voltage CPU, in which a CPU can supply a different output voltage than the input
• 42-volt electrical system, automotive wiring, where some implementations run combined 14V/42V electrics
• Mains electricity, for North American household 110V/240V grid power systems