Toa DP-SP3 - Manual (Page 70)

70
(5) Channel Select
Select the target channel of which control output volume and output mute are to be controlled.
(6) [Disable] button/ [Enable] button
Clicking the [Disable] button disables control from the Contact input, turning into [Enable] button.
Preset number of the controls performed before clicking the [Disable] button is retained, but both output
volume and output mute controls are cleared.
To control again, click the [Enable] button.