EXTernal will output a burst 
waveform after each external 
trigger pulse. Any additional 
trigger pulse signals before the 
end of the burst are ignored.  
If the APPLy command was used, the source is 
automatically set to IMMediate. 
The *OPC/*OPC? command/query can be used to 
signal the end of the burst. 
If the trigger source is set to manual, the function 
generator outputs a burst count waveform with 
the specified number of cycles each time the 
trigger signal * TRG is received. The function 
generator stops and waits for the next trigger after 
the specified number of cycles has been output. 
You can configure the function generator to use an 
internal trigger to start a burst or send a trigger 
signal from the rear panel port connector by 
pressing the front panel key and you can also send 
a trigger command * TRG through the remote 
interface to provide an external trigger source.