International Institute of Cricket Umpiring & Scoring
That is the theory behind calls. The practice is sometimes very different. Batsmen will often forget whose call it is supposed to be, with one running and the other rooted to the spot - and woe betide the tailender who runs out the team's star striker!
Some batsmen are notoriously unreliable in their calling, often leading to confusion and catastrophic run outs. The famous England player Dennis Compton was a prime offender, apparently. It was said of him that 'a call by Compton was merely an invitation to open negotiations on the subject!'
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