Batboard

I have an HLN6412A for a MCS2000 dual head installation, and the accessory connector was disconnected and one of the pins pulled out of the accessory connector, and i can't tell where it goes. I've looked @ all the (limited) MCS2000 installation stuff, and the programming connections, and i have a yellow wire which has a female pin end for the accessory connector that i can't identify. I've identified and confirmed pins 1,2,4 -> 9,10,11, 14 on the connector, but still have this yellow wire doing nothing which obviously belongs somewhere. Any ideas?

....and we can close this one, it's switched B+ which drives the amplified speaker in the setup. Connects to pin 14 on the accessory connection. Thanks for looking.