[nditada]

Hi! author here, funny to read this 11 years after! I'd be happy to provide more details. You can mail me at my username @ domain of the post.

And yes, the title was awful simonw!

[thatthatis]

How does the encoding work? Did you write up the algorithm separately?

[nditada]

The encoding used a prime number as a factor of the number reported, i.e. the ordinal number of each option is multiplied by that prime factor. The prime was selected as the largest possible number based on the max digits to send and the number of options to encode. That created a sparse distribution of possibilities, so that typos were more probable to get detected. It also enabled that by simply factoring the report and using the factors to identify the type of wheel that was sending the reports, allowing one single phone number to receive reports from multiple wheel types or versions.