User manual
Chapter 2 Command System RIGOL
DS4000E Programming Guide 2-29
Remarks
When <source> is set to "OFF", it indicates that TX source channel is not set.
TX source channel and RX source channel (refer to the :BUS<n>:RS232:RX command) cannot be both
set to "OFF".
Return Format
The query returns CHAN1, CHAN2, CHAN3, CHAN4, or OFF.