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The WR-4 will also allow control of the output channel volume using the two lower keys. To select an input audio source, simply press one of the six corresponding input select keys. Multiple input sources may be assigned to a single select key, and also multiple selected keys may be engaged at a given time. Select keys that are currently engaged will have their corresponding LED lit. To deselect an input source, simply press the corresponding key again. To change the output volume, simply scroll