I'm not aware of any regulations governing on-call time, there could be some individual states that have them. Different businesses and industries have differen

I'm not aware of any regulations governing on-call time, there could be some individual states that have them. Different businesses and industries have different practices. For hourly employees, labor law probably requires some compensation at least when a call comes in. For salaried people, compensatory time when a call comes in could be an option but often times the idea is being on-call sometimes is factored into your regular pay.