NF DP420LS Instruction Manual page 187

4. Advanced Operation
 Enabling/disabling external control function
1. Press the MENU key to move to the root menu, then select [System]. The system setting
window opens.
2. In the [Ext Control] item, select [1: Disable] or [2: Enable]. See 4.18.2 about [3: DevCtrl].
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168 PROGRAMMABLE AC POWER SOURCE