# More on Four-digit Mnemonic Number Systems

I just saw that Ben posted a blog post about his progress with a four-digit number systems:

And then there’s the continuing dilemma of the four-digit number system. I have a nagging doubt that after all the effort of creating it, it’ll turn out to be unusable and I’ll have wasted a lot of time and made myself even worse at memorising numbers than I was in the first place.

Simon Reinhard also left a comment about his four-digit system.  He may be the first example of someone putting a four-digit system to use at the highest level of competition. (He holds the world record in speed cards.)

## A 4-digit PA System?

One other thing I’ve been thinking about:

I wonder if a PA system could function as a four-digit system:

• 1921 – “TUHNI” – woodpecker bouncing up and down
• 1922 – “TUHNU” – woodpecker pecking an onion
• 1923 – “TUHNAA” – woodpecker walking on water
• 1924 – “TUHNA” – woodpecker on fire (like the Human Torch)

Could three 4-digit compound images then be placed into each locus?

Would it be possible to build six-digit compound images (PAO) and place 18 digits per locus? For example, could three compound images like this be placed in one locus:

• 192120 – “TUHNISO” – woodpecker bouncing up and down on a blackboard

Would it work better if it weren’t a strict PA or PAO system, but were designed so that the compound images interact with each other better?

If a two-digit PAO system could be modified into a method of placing 18 decimal digits per locus, then a three-digit PAO-type system could theoretically put 27 decimal digits in a locus with only 1,000 basic images.  Using that idea with Ben’s binary system, one locus could theoretically hold 90 binary digits.

Just brainstorming out loud… 🙂