From Longman Dictionary of Contemporary Englishbe on callbe on callWORK/DO WORKif someone such as a doctor or engineer is on call, they are ready to go and help whenever they are needed as part of their job Don’t worry, there’s a doctor on call 24 hours a day. → call
Examples from the Corpus
be on call• Doctor Lalor won't be at the surgery this afternoon, but she's on call until midnight.• If the machine breaks down at any time, there's always a technician on call.• She's on call at the hospital every other night.• There are four physiotherapists on call at the sports injury clinic.• Resident managers live in hotels and are on call 24 hours a day.• The employees are on call seven days a week, 24 hours a day to respond to emergencies.• In addition to their regular schedules, chief executives are on call at all hours to handle emergencies.• Construction managers must be on call to deal with emergencies.• A federation representative is on call 24 hours a day by mobile phone.• She was on call to open and shut the gates at any hour, in any weather.• The tour director usually stays in the hotel with the group, to be on call if anything should go wrong.• He assumed that a porter or janitor was usually stationed there to be on call or to answer enquiries.• Arrange things so that there is always some one in the building who is on call for machine problems.• As a doctor, you will be on call regularly at weekends. 