Alesis DM Pro Reference Manual page 152

Advanced Trigger Information
This option looks pretty strange, but it's the way to use the AUX Pedal Input for
muting Drums or Cymbals with a rimswitch trigger pad and still be able to play two
separate pads on TRS Trigger Input jacks 7/8 or 9/10. This involves two different
kinds of Stereo Instrument "Y" Cables (sometimes called "TRS splitter cables"): one
with two socket or "female" mono 1/4" jacks on the opposite end, and another with
the more standard set of "male" mono 1/4" jacks.
Here's how to hook it up. Plug the TRS-to-female cable into one of the TRS Trigger
Input jacks (7/8 for this example). Plug the other TRS cable into a dual-trigger pad
equipped with a rimswitch trigger. The mono "male" end which is marked "RING"
should go into the AUX Pedal Input jack. The other mono end, marked "TIP", should
be plugged into the "female" end which is marked "TIP" on the other TRS cable. The
other mono "female" socket needs to be plugged into a standard guitar cable (1/4"
mono), which itself can then be plugged into the mono pad.
Once hooked up correctly, the center of the rimswitch pad should be triggering the
Cymbal assigned to Trigger 7 and the mono pad should be triggering the Cymbal
assigned to Trigger 8. Remember, whichever Cymbal you want to be able to "choke"
with the rimswitch must be assigned to the same Mute Group number as the
rimswitch. And of course, you can assign all three to the same Mute Group if you
wish. For a description on what this means and how to do it, refer to that section in
"Chapter 4: Programming Drumkits."
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RO EFERENCE ANUAL