Alesis DM Pro Reference Manual page 149

You can use two separate pads or trigger sources to trigger two different Drums via
the TRS Trigger Input jacks on the back of the DM Pro. Generally, in the DM Pro's
preset Drumkits the TRS Trigger Inputs are used for grouping similar percussion
instruments. Triggers 2 and 3, for example, which share the first TRS jack from the
left as you're looking at the rear panel, are set up for a Snare and a Sidestick Snare,
respectively. Triggers 13 and 14 are assigned the task of triggering two different sets
of Hi-hat Drums ("center" and "edge" hits, respectively). But you can use any Drum
on any Trigger, if you like.
The TRS jacks are used to reach Trigger Inputs 2/3, 7/8, 9/10, 11/12, and 13/14.
DM P R M
RO EFERENCE
If for some reason it is necessary to leave one of the mono ends of a
TRS splitter cable "dangling", or unplugged, turn the Threshold for
its Trigger up to 00 to help prevent false triggering of the Trigger
Input which you intend to use.
ANUAL
Advanced Trigger Information
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