red signal

基本解释

When we are driving, and we see red signal, we often are more alert.
当我们开车，看到红色的信号时，总会提高警觉。
This system, Positive Train Control (PTC), is intended to stop or slow a train automatically if a driver goes too fast or passes a red signal.
这套系统称作列车“自动控制系统”，当列车车速太快或司机擅闯红色信号灯时，这套系统就会让列车停下来或自动减速慢行。
Using the natural reflectivity of ceilings and walls, a transmitted infra-red signal can be received by any number of receivers within a room.
利用天花板和墙面的自然反射性，传送的红外信号能够被一个屋子里的所有接收器接收到。

This system, Positive Train Control (PTC), is intended to stop or slow a train automatically if a driver goes too fast or passes a red signal.
ECONOMIST: American railways
The birth and death phases of stars, for example, are associated with heavy dust clouds that give off an infra-red signal which might resemble the swarm of artificial satellites constituting a Dyson sphere.
ECONOMIST: Is it time for a new approach to finding extraterrestrials?