Abstract
In a compressed air braking system for commercial vehicles the distribution of the compressed air for storage, the pressure at which it is stored and the quality of the air in terms of its cleanness and dryness is of paramount importance. Traditionally this has been achieved using a number of individual components ¨C unloader or governor, air dryer, multi-circuit protection valve ¨C which over a period of time have been integrated with each other. First the unloader was integrated into the air dryer (¡Ö1980) then the multi-circuit protection valve was ¡®attached¡¯ (¡Ö1996) with the resulting device being termed an ¡°Air Processing Unit¡± (APU). Now with the ¡°Electronic Air Control¡± (EAC) device the multi-circuit protection valve function has been fully integrated.