It’s not a PA system… in PA, the first card gives you P and the second card gives you A. 2-card system require a lot more images than PA or PAO systems do.
The Ben System has a single image for every possible two card combination. The suit combination is the first consonant, the first card’s rank is a vowel that follows, and the second card’s rank in the second consonant. See here for more detail and another 2-card system: