Taking Gonk's suggestion I logged a question to the Outlaw support site. I received the answer this morning from one of their support techs Edward. Here's the answer:

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Bill,

You can use the trigger 2 connector for that purpose (just make sure to turn the trigger 2 output "On" for every source from within the Input Config menu of the Model 990).

For connection to the Xantech unit you mention, simply cut off one end of your trigger cable and strip back the wires. A standard mono mini trigger cable is a two conductor wire (positive and negative). The wire running in the middle of the cable is your positive lead. The outer wire, is your negative lead.

Connect them accordingly to the Xantech, and you should be all set!

Just make sure that you do not have the trigger cable connected when making your splices.

Thanks and Regards,

Edward

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I'm off to Radio Shack (in the morning).

BillMac