機場捷運的號誌是全國率先使用戶外天線當作無線電傳輸媒介的鐵路運輸系統，而世界各國捷運號誌早已有採用戶外天線傳輸的案例，如義大利Milano Line1、西班牙Malaga L1&L2等等。
The signaling system of TIAA MRT is the first in the country to use outdoor antenna as a radio transmission medium of the railway transport system. In contrast to Taiwan, countries around the world have long used outdoor antenna transmission, such as Milano Line1 in Italy, Malaga L1 & L2 in Spain and so on.
The Radio Transmission System (RTS) is the medium that provides communication between the equipment room and the train (transmitting control signals and information). The system uses 2.4GHz Ethernet spread spectrum radio system with anti-interference characteristics.
The RTS is composed of three main blocks:
1.Equipment in the signaling facility room: includes HDLC / IP converters and Ethernet switches. The equipment use optical fiber to connect with wayside radio equipment, as shown in the upper half of Fig. 1.
2.Wayside radio equipment: includes fiber / Ethernet signal converter and 110V power supply. The signals are transmitted respectively to the two antennas in the opposite direction via the splitter, as shown in the lower half of Fig. 1. Each adjacent antenna will have a distance of about 50 to 250 meters. The installation principle for the antenna is that the coverage of two antennas, A and C, which is before and after antenna B, must cover antenna B in order to achieve the purpose of redundancy, as shown in Fig. 2.
3.On-train radio: includes mobile radio and HDLC / IP converters.
The radio antenna has the appearance of mesh or flat plate. The mesh antenna is suitable for the elevated section; the flat antenna can be applied to the elevated section and the tunnel section. The signal transmission distance is about 300 meters to 1,300 meters.