Editing Diode (section)

===Current steering===
Diodes will prevent currents in unintended directions. To supply power to an electrical circuit during a power failure, the circuit can draw current from a [[Battery (electricity)|battery]]. An [[uninterruptible power supply]] may use diodes in this way to ensure that the current is only drawn from the battery when necessary. Likewise, small boats typically have two circuits each with their own battery/batteries: one used for engine starting; one used for domestics. Normally, both are charged from a single alternator, and a heavy-duty split-charge diode is used to prevent the higher-charge battery (typically the engine battery) from discharging through the lower-charge battery when the alternator is not running.

Diodes are also used in [[electronic keyboards|electronic musical keyboards]]. To reduce the amount of wiring needed in electronic musical keyboards, these instruments often use [[keyboard matrix circuit]]s. The keyboard controller scans the rows and columns to determine which note the player has pressed. The problem with matrix circuits is that, when several notes are pressed at once, the current can flow backward through the circuit and trigger "[[Keyboard (computing)#Control processor|phantom keys]]" that cause "ghost" notes to play. To avoid triggering unwanted notes, most keyboard matrix circuits have diodes soldered with the switch under each key of the [[musical keyboard]]. The same principle is also used for the switch matrix in solid-state [[pinball machine]]s.