ISO 7634:2003 specifies procedures for testing the compressed-air braking systems of full trailers, semi-trailers and centre-axle trailers, with and without antilock braking system (ABS), corresponding to road vehicles of Category O as defined in UNECE R.E. 3.
You easily download any file type for your device.ISO 7634:2003, Road vehicles - Compressed-air braking systems - Test procedures | ISO/TC 22/SC 2. I have read it a couple of times and even shared with my family members. Really good. Couldnt put it down.