On-callWhat it means, in plain English

On-call means being available outside normal working hours to respond if needed, common in maintenance, healthcare, utilities and IT. Whether on-call time counts as working time in the UK depends on the constraints imposed; time spent required to be at or near the workplace generally counts, while being reachable at home generally does not until called out. On-call allowances and call-out rates are contractual, and any hours actually worked count towards working time limits and minimum wage calculations.