Control theory is a branch of mathematics and engineering, which defines the conditions needed for a system to maintain a controlled output in the face of input variation. Classically developed for ...

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Editor's note: On December 11, we reviewed all of the items in this guide and removed anything that won't arrive in time for December 25. Looking for the perfect Christmas gift for the runner in your ...

Want more tried and tested recommendations from the RW editors? Sign up to our monthly newsletter Kit Bag. Click here to subscribe. Editor's note: We updated this page on 17 December 2025, in line ...