What do you use the Honeywell 12612 Power Supply for?
You will use the 12612 power supply circuit board if you are going to use more power than the Vista supplies via the auxiliary power terminals. The Honeywell Vista systems can supply 600mA of power for devices.
We recommend staying under 10% of the maximum of 600mA. If you're going to go over that then the 12612 will be needed.