User`s guide

Remarks
After selecting the trigger source, you must place the instrument in the
"wait-for-trigger" state using the INITiate or READ? command. A trigger
will not be accepted from the selected trigger source until the instrument
is in the "wait-for-trigger" state.
For the IMMediate (continuous) source, the trigger signal is always
present. When you place the instrument in the "wait-for-trigger" state, the
trigger is issued immediately.
For the BUS (software) source, the instrument is triggered by the *TRG
command received over the remote interface. The *TRG command will not
be accepted unless the internal DMM is in the "wait-for-trigger" state.
For the EXTernal source, the instrument will accept a hardware trigger
applied to the rear-panel Ext Trig Input BNC connector. The instrument
takes one reading, or the specified number of readings (sample count),
each time a TTL pulse (low-true for slope = negative) is received. If the
instrument receives an external trigger before it is ready to accept one, it
will buffer one trigger.
The INTernal source is only available for the 34411A and L4411A, which
provides trigger level capability. To trigger on a level on the input signal,
select INTernal for the source, and set the level with the TRIGger:LEVel
command. This syntax is not available on the 34410A.
The CONFigure and MEASure? commands automatically set the trigger
source to IMMediate.
The instrument selects the IMMediate trigger source after a Factory Reset
(*RST command) or an Instrument Preset (SYSTem:PRESet command).
It is recommended that all triggered measurements be made using an
appropriate fixed manual range. That is, turn autorange off
(SENSe:<function>:RANGe:AUTO OFF), or set a fixed range using the
SENSe:<function>:RANGe, CONFigure, or MEASure command.
If the selected trigger source is invalid due to a settings conflict, the source
reverts automatically to IMMediate on an INIT. A settings conflict error
message is also generated.