service signal

例句：

1. 1.The service signal is clear, so we can proceed with the operation.
   服务信号清晰，我们可以继续操作。
2. 2. The service signal is a crucial part of the communication system.
   服务信号是通信系统的重要组成部分。
3. 3. The service signal was sent to all the stations in the area.
   服务信号被发送到该地区的所有站点。