How does a pneumatic temperature control system work.?

I have never had to work with a pneumatic temperature control system but have seen some working ones. The first temperature control job I was on I was removing a honeywell electronic contol system (which was the first temp control system to replace the original pneumatic controls) and replacing it with a Trane system with 581 controllers and expansion modules. Now I am on a job with Johnson Controls. The job I am currently on at Indiana University of South Bend JCI is redoing a pneumatic contol system and I wanted to know how it works. Specifically the freeze stats (low temp stats), and the zone thermostats. If you have any information on any part of the system or the whole system I would like to hear what you have to say.