backup relay

例句：

1. 1. The backup relay is essential formaintaining network stability during power outages.
   备用中继器在电力中断期间维护网络稳定性至关重要。
2. 2. The engineers replaced the oldbackup relay with a more modern model.
   工程师们用更现代的型号替换了旧的备用中继器。
3. 3. The backup relaywas designed to automatically switch over to themain line in case of a fault.
   备用中继器被设计成在故障时自动切换到主线路。