Remote Triggering a ION via a voltage source

Ion has a relay input that you could use. It's written up in the wiki. As an alternative, Ion has a serial port and a syntax for serial strings. It may also be possible to use the ethernet connection in which case UDP strings could be used to trigger the Ion.

I'm sure someone will correct me if I'm wrong, but I don't think the serial ports on Ions actually do anything- AFAIK, if you're talking strings, and heading directly into a console, serial strings over UDP are the only way in.

For the OP's application, it sounds like the remote trigger port may be the way to go!

Midi will add another layer of complexity that is unnecessary in your system

The ION has a remote trigger port with contact closure inputs and a relay output that can be programmed to run various actions.

See the great Wiki ETC put up http://community.etcconnect.com/wikis/products/ion-and-element-relay-out-and-contact-closure-inputs.aspx

Can you provide the model number of your Christie Device?

Most christie automation devices have GPIO (the 12VDC signal output) as well as a relay output

If you can use the relay output,

Hookup the ION's contact closure inputs to the relay output (for instance pins 1 and 14)  http://community.etcconnect.com/wikis/products/ion-and-element-relay-out-and-contact-closure-inputs.aspx

The christie relay will close the circuit between the ION's 12vdc+ pin and contact closure pin

If you need to use the voltage signal I would purchase a relay to isolate the devices from one another, and incase I am mistaken that both devices used 12vdc signals

Purchase a relay with coil rating that corresponds to the christie's voltage output

Attach the christie voltage signal to the input (coil) side of the relay

On the output (switched)  side of the relay you would attach the ION's contact closure input, again for instance pins 1 and 14.  

Also if you plan on using the ION's remote trigger port often, buy a d-sub cable and breakout board (there are many, but an example is http://www.winford.com/products/brksd15.php ) 

They usually have solid screw connectors that are easy to troubleshoot and you save the hassle of making your own d-sub connector, or trying to use the tiny gauge wires inside a purchased d-sub cable. 

$20 is worth it.

Thanks, I thought the ION could do this but couldnt actually find it any were when I searched, couldnt even see it in the manual.