We test the top home security systems to find the best for you. Our tech critic includes alarm and camera kits from Simplisafe, Yale, Tapo, Ring and Eufy.

The maximum lifetime obtained when using any combination of chains is shown to be upper bounded by the solution of a suitable linear programming problem. The upper bounds show that the proposed method ...

Use BBC.com or the new BBC App to listen to BBC podcasts, Radio 4 and the World Service outside the UK. Find out how to listen to other BBC stations ...