Military Man, I think I now know where you are coming from regards pneumatics !!!! Yes the give a way was the water trap and dehydrator. One A/C that comes to mind is the F27 (not the -50).Engine gearbox driven compressor (4 stages) 2 pipes off the compressor (3rd and 4th stages) 4th stage goes through the water separator,dehyradrator and is then t-ed into the regulator and main supply (the regulator dumps 3rd stage when the required pressure is obtained,reducing load on the compressor)Air is then supplied to a common supply pipe (individual check valves per engine) to All 3 bottles at the same time (main,emergency and brake bottles)ensuring they are equal.On the F27 there is an Isolation Bar which can be pulled which will isolate the main bottle and the brake bottle so the emergency bottle can be charged up first.Emergency down-pressure is the same as normal down except it uses different plumbing.Emergency braking bypasses the Maxarets(anti-skid) and reaches full pressure in a pre-determined time,so its either on or off depending on how long it has been selected on (pressure gauges tell the crew how much line pressure is being supplied) In the emergency brake system there is a pressure reducing valve and a on-off control valve.
I hope I've answered the question with-out confusing you too much
Cheers