Tenma 72-10175 User Manual page 51

CH1: Select CH1 as trigger signal
CH2: Select CH2 as trigger signal
CH3: Select CH3 as trigger signal
CH4: Select CH4 as trigger signal
EXT: Select EXT as trigger signal
Slope: Set the slope to Rising (+) or Falling (-).
Rising: Trigger on rising edge
Falling: Trigger on falling edge
The user can also change the trigger setting on trigger panel in sidebar.
High Frequency Rejection
Select "HF Rejection" in "Trigger Setup" window