Updated Already » Back half of Thermostat

The terminal block connects the Red, White, Yellow and Green wires from the house HVAC lines. (Black is the new Yellow.) The two white boxes are the Heat and Cool relays. The maroon 6-pin connector and the white JST connector are how the front and back halves join up. And the black doohicky in the lower right is the 2.1mm power plug. Power can alternatively be tied in via the terminal blocks.