Looks to me if you got a +12 volt supply arriving from the battery which supplies +12 volts to unit 143. The +12 volts also goes down via the fuse to supply the ignition switch. From the ignition switch you will have a +12 volts out when the engine is cranking only suppling the idle adjustment motor (145)
The other wire is another +12 volt feed via a fuse which is supplying units 256 and 150.
Hope that helps