= Patent =
For one reason or another, Amstrad has patented the verification mechanism ([[Media:Patent GB2243701A.pdf|GB2243701A]]). The patent seems to focus on ''verifying'' (rather than on ''sending'') the sequence, so its legal use is a bit unclear.
On the [[Original Arnold V Specs]] - Issue 1.5 - 10th April 1990, it is precised at §2.11 "Locking of enhanced features":