When the internal or external trigger is selected, the
trigger output signal will be at either a TTL low/high
level and will toggle when the specifed number of
waveform cycles completed.
When the manual trigger is selected, the trigger
output turns on at the trigger soft-key be pressed.
When the manual trigger is selected, the function
generator automatically disables the trigger output.
When using a manual trigger, the function generator
outputs a pulse wave (>1us) from the Trig Out
terminal.