It is a Matrix Audio MRC 8e (8 zone distributed audio system). Here's a link to the manual. page 42 details the rs 232 codes/protocal. I am controlling this device with a Vantage system. There is an option in their programming software that allows me to send a "serial string" via rs 232 directly to the Matrix Audio device.

[Link: drivehq.com]

Thanks for any help you can provide