spare channel

例句：

1. 1. The company uses spare channels to ensure that its services are available even during peak traffic hours.
   该公司使用备用频道以确保其服务在高峰时段仍然可用。
2. 2.In times of crisis, the government often relies on spare channels to communicate with the public.
   在危机时期，政府经常依赖备用频道与公众沟通。
3. 3. The team decided to use a spare channel to send their emergency message to the affected area.
   团队决定使用备用频道向他们受影响的地区发送紧急信息。