* T3 keeps passengers in railroad cars safe.
* In those places in which radio environment is weak and wire announcement is not allowed (such as in a subway and in a train)
* Wireless announcement becomes possible by using the radio relay system with low power in case of emergency situation.
* T3 is the solution for wireless announcement
* T3 is the system that makes an announcement to passengers even if the power is cut off in case of emergency.
* It is because devices with built in rechargeable batteries are installed in railroad cars and voice packet is relayed for receiving & transmitting by the digital wireless relay method of installed devices.