A/C vacuum actuator kick panel question

[OUbesto]

I am restoring the interior on my '70 C-10, 402 with factory A/C. The passenger side outside outside kick panel air vent appears to be controlled by a vacuum actuator versus the driver's side that is controlled manually by a pull-type knob.

First question...is this correct? I am assuming the passenger side vent is somehow controlled by the 4 season A/C system? Can anyone tell me how it actually works?

Thanks for any help anyone can provide.