The patent seems to focus on ''verifying'' (rather than on ''sending'') the sequence, so its legal use is a bit unclear.
On the official "[[Original Arnold V" specificationSpecs]] - Issue 1.5 - 10th April 1990, it is precised at §2.11 "Locking of enhanced features":
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it should be noted that unauthorised use of this mechanism may infringe Amstrad's patent.