机车信号，又称车上号志、车内号志或车载号志，是自动显示列车运行前方地面信号机显示的机车车载系统。

• 地面设备
  • 信息源：地面信息发送设备。
• 车载设备
  • 信息接收：感应器接收地面钢轨中传输的信号。
  • 信息处理：处理感应器接收到的信息。
  • 信息显示：显示信息处理结果。

Cab signalling is a railway safety system that communicates track status information to the cab, crew compartment or driver's compartment of a locomotive, railcar or multiple unit, where the train driver or engine driver can see the information continuously.