Definition
Being 'on call' refers to the state of a worker, particularly in professions like medicine, where one is available and prepared to work or make official visits whenever needed.
（尤指医护人员）随时待命，值班的
The surgeon had to be on call all weekend to handle any emergency situations.
那位外科医生整个周末都必须待命，以处理任何紧急情况。
Due to staff shortages at the hospital, nurses often have to be on call to support the needs of the various wards.
由于医院人手不足，护士们经常需要待命以支援各个病房的需求。
The tech company's support team must be on call 24/7 to address any client issues.
这家科技公司的支援团队必须24小时待命，以处理客户的任何问题。