on call基本解释
adj. 随叫随到的，待命的

例句：
I have a messenger on call .
我叫人给你送过去。

Acupuncture can also help but you 'll have to arrange ahead of time to have a therapist on call when you go into labor .
针灸也可能会有帮助，但需要在进入临产时，提前电话预约好治疗师。

At least miranda will be in miami so we don 't have to be on call this weekend .
至少米兰达会在迈阿密，这个周末不会接到电话了。

Escalate unresolved calls to the appropriate support resource and follow up on call resolution .
对于逐步上升的未能解决的电话给予适当的支持，并且一直跟踪解决电话问题。

I 'm surprised to see you here.you on call tonight ?
在这里见到你我很意外你今晚值班?