Sets whether constant current will be controlled externally.
|Value||NONE||External control is not performed (factory default)|
|VOLTage||Controls the current using an external voltage|
|RESistance||Controls the current using an external resistance|
For the setting that is applied when *RST is sent, see this table.
Returns whether constant current is being controlled externally in CHAR format in response to CURR:EXT:SOUR?.