Re: Yamaha digital to analog gauge wiring
When something triggers an alarm state that wire goes to ground. A 2 wire buzzer/horn can be connected with one side to key-on 12vdc (usually a purple wire) and the other horn wire connected to your green/red wire. When a fault triggers an alarm state and the green/red goes to a grounded (-12vdc) state the alarm will sound.
I've got the SmartCraft system and it has a similar brown/blue wire that I hooked up to a red LED on my dash. I already have a horn in my control that sounds for the basic engine problems. I was kind of suprised to find that the LED would light for several alarms that were being triggered by the SmartCraft gauge and not just the normal engine alarms. It's kind of nice having that blinking red light indicating low fuel, trim above 20 degrees, etc.
Just as a side note, until I put that LED in I was considering going back to all analog gauges but I've since changed my mind.