1977 Coupe Deville 425..........4-port Thermal Vacuum Switch, how does it work?

My 1977 Coupe Deville 425 has a 4-port Thermal Vauccum Switch mounted in the front of the engine that operates on a heat signal from the water jacket.

The TVS has 4 ports:

1. line from ported vacuum in Rochester Quadrajet.
2. line from port diectly into intake manifold.
3. line directly to EGR valve
4. line directly to vacuum advance unit on distributor

How are the two different vaccuums routed to the two vacuum actuators inside the TVS itself?

Thanks for your help.

Tich.