The difference between the Cheater Valve and Air Regulator

Air Pressure Regulator:

http://www.neu-master.com/Air-Regulator-pl589700-p2.html

A air pressure regulator is a control valve that reduces the input pressure of the air to a desired value at its output. The pressure regulator's primary function is to match the flow of air through the regulator to the demand for the compresssed air placed upon it, whilst maintaining a constant output pressure.

     If the load flow decreases, then the regulator flow must decrease as well. If the load flow increases, then the regulator flow must increase in order to keep the controlled pressure from decreasing due to a shortage of air in the pressure system.

Air Cheat Regulator /Cheater Valve

http://www.neu-master.com/ACR-Series-Air-Cheater-Regulator-pd6725519.html

It's a control valve which through adjusting the discharge area to regulate the flow rate . 

Sometiems , for a spray gun , a cheater valve is enough to make it working , why ?

Please see the following picture , there is already a air pressure regulator on the air compressor :

So we could set the output pressure on the air compressor by the regulator. 

But if there is no the air regulator on the air pump , then for a spray gun , we must prepare a specialized air regulator for it . and the meaning time a cheater valve is essential.

In one word, the air regulator is for seting the output pressure , and the cheater regulator is for chontrol the flow rate .